Check out the help center.  You can search by word or just browse.  All of the rules are in there!

Try this one   http://www.paperbackswap.com/help/search.php?terms=not+allowed

Welcome to PBS.

You might want to take some time to browse through the Help Center (there's a link to it on the top of every page).   To answer your question,  an unpostable book is one that is not allowed to be posted or does not meet condtion guidelines.  Since condition is the more common complaint, I've copied the help page for it along with the link.

Writing on the page edges has been discussed before, and a name has been determined to be OK.  I can't find the link now. 

What types of books can be posted:  http://www.paperbackswap.com/help/help_item.php?id=204

Book Condition guidelines:  http://www.paperbackswap.com/help/help_item.php?id=205

When you post a book, you are asked to confirm that the book is "in good condition, and not excessively worn".  It is impossible to list all of the ways in which a book might be considered excessively worn, but the criteria below are as comprehensive as we have been able to make them.

If you feel your book falls into a "grey area", you can either post the book and send a Personal Message to the requestor, or not post the book.  We have delineated what we can, and we expect members to follow these guidelines, and use their common sense in cases that are unclear.  If you would not mind "paying" a credit for a book you are considering posting, then it is probably okay to post.  However, book condition can be a subjective matter.  Keep in mind that a pattern of sending out poor-condition or inappropriate books will jeopardize a sender's membership.

All of the information below apply both to swapping for credits and Box-O-Books swapping.

General remarks:

• This is a used-book swapping site; books are not expected to be in like-new condition.
  • Older books may have some page yellowing or spine-creasing or dogeared pages; these are all OKAY.
  • Decirculated library books may have various markings and/or stamps inside or outside or on the page edges of the book; this is OKAY.
  • Bookcrossing books may have stickers or stamps or markings on the outside or inside covers or page edges of the book; this is OKAY.
  • Hardbacks do NOT have to include their dustjackets.
  • Audiobooks MUST be the original cassettes/CDs, but do NOT have to include the outer "box" that held the set.
  • Audiobooks must be playable.
  • There is an exception to general condition guidelines for textbooks; see below.
  • There is an exception to general condition guidelines for cookbooks; see below.

• We do NOT have a place for members to describe the condition of a particular copy of a book.
  • ALL books on PBS are expected to be in "good, not excessively worn" condition
    • note the specific cases for textbooks and cookbooks
  • Books are requested in FIFO (first-in, first-out) order
• If you would like your books to be in "better-than-PBS" condition :
  • You are responsible for setting Requestor Conditions on your account.

Guidelines:                                                                                                                                       

Overall Condition:

• No damage at all from water or other liquid
• Not soiled
• No stains (exception for cookbooks--see below)
• No mold

Cover:

• Must both be present (front and back)
  • note that a paperback missing its front cover is  usually an illegal, unsold copy
  • "cover" does not = dust jacket.  Hardcovers do not need to include their dust jackets to be swapped here.
• Cover not torn
  • some used book stores cut out a small part of the cover; if the amount missing is less than 1 inch, this is OKAY
  • a small rip (less than 1 inch) in the cover is OKAY
• A bookplate inside the cover or on the flyleaf is OKAY

Binding:

• Must be intact, with no separation on the inside or outside of the book
• If the book tends to open at a particular page, this is OKAY
• Small amount of fraying or denting at top or bottom is OKAY

Pages:

• No torn pages
• No loose or missing pages
• No writing or highlighting on text pages
  • a signature or note on the flyleaf is OKAY
  • an author's signature on the title page is OKAY
  • writing or highlighting on the text pages is NOT OKAY
    • Exception: if it is a textbook or workbook, these are expected to have highlighting/writing
      • if you post a textbook/workbook, the condition must be described to the requestor in a Personal Message
      • AND the described condition MUST BE AGREED TO before the book is sent
      • This is the one of the ONLY two cases in which a PM exchange about a book is required before the book can be sent(the other is for cookbooks--see below).

• No staining

  • Exception: Cookbooks may have some mild staining, since these are used in the kitchen and while cooking, and some minor degree of staining could be expected in a used cookbook.
  • HOWEVER, if you post a cookbook and it is stained, the condition must be described to the requestor in a Personal Message
  • AND the described condition MUST BE AGREED TO before the book is sent
  • This is the one of the ONLY two cases in which a PM exchange about a book is required before the book can be sent (the other is for textbooks--see above).
  • this exception applies to the covers of cookbooks also.

Supplementary/Accompanying Materials:

• Books that require non-Media supplementary materials may not be posted

  • an example would be a book that requires a decoder or craft materials
  • these items cannot be sent MediaMail
• Books that require supplementary Media materials may be posted
  • supplementary Media materials include CD(s)/CD-ROMs/DVD(s)/VHS tape(s)
  • if so, the supplementary must accompany the book if the book originally included them

.

It depends on where the writing is.  The name/autograph can be on the front title page but I'm not exactly sure what you mean by the "page edges."  If it's randomly internally then no, that's not allowed.

Ex-library books and book crossing book have different criteria than regular books when it comes to stickers/ink stampings. Same with textbooks and markings/highlightings.  That is why those three are specifically mentioned.

Do not take a guess and don't go with the "I imagine it's okay" theory. That's not fair to others on this site. If you're not sure, ask before sending.  People get mad on here, and rightfully so, if they receive an unpostable book - take a look through this forum for the past posts about sending unpostable books.  They may ask for their credit back.

Look through the help center thoroughly but here is what I found on page markings (it's also posted above by another poster:

Oh! Boy, that's a new one! lol I'm sure it would still fall under the "no" category of not being postable for a regular book.

Remember though that textbooks and regular books, including reference books, don't have the same rules so it's confusing when you say textbooks/reference books. If it's a textbook then full disclosure of highlighting/writing  has to be done before mailing per the PBS rules.  If it's a reference book, not listed as a textbook, then it's not postable. To be honest with you, I wouldn't want the type of writing you mentioned but that's just me. Someone else  might not have any issue with it.

Beware though, if you offer to take the book back then that'll probably cost you two credits. One for the original book that you don't get and one to offer the person to cover the postage. Mistakes are costly in terms of credits on her, at times! lol

It sounds like you have it under control though - good luck to you! Hopefully the receives won't have a problem with the books.

this exact thing has been brought up in the past and it was stated by R&R that it was OKAY to post. 

Kristen - It's okay on regular books? That's surprising since it says in the guidelines that only a name or signature on the fly leaf or title page is OK. Why would someone want huge letters written on the outside edge (opposite the binding) on a regular book that they might be keeping for a library or such? That truly mars then entire outside look of the book, IMHO.

If that's the case, I see my first set of conditions coming up.

Name on the edge of a book was discussed in the forums and Robert said it was OK.

Amy, every time you list a book, you are asked if the book meets posting guidelines, and they are listed.  Take a little time to read through those sections before you click through each one, and you will save yourself a lot of grief.

I'm still surprised - someone should add that to guidelines since it is vastly different than having a signature or name on the title or fly leave page.  Thankfully I haven't run into that yet - I'd be a bit disappointed. But then I can't imagine it's done too often on regular books.

I would imagine if someone did it in a heavy marker it would be rather ugly, but what's the difference if someone's name is there or the library has stamped all three directions of the edges with their stamp?  And that's basically what the discussion boiled down to, that is really isn't that different from allowing bookcrossing or library stamps on the closed edges of the pages.