The title pretty much says it all! I can't always rummage through my books to make sure I'm not double requesting a book I already have. This is especially difficult when you're trying to get all the books in a series and the covers all look similar. 

Also, can I do a WL search and offer people books that I have to swap that are on their WL?

You can view this on your Transaction Archive.  You are able to sort it by books you've requested, date, & such.

As for the WL search, the only way is to look on a persons profile.  You must have someone in mind though.  If not, then you would just post it in the system.

Kellie

If you request a book that you have requested in the past, you get a notification of that when you request the book again.

If you type in the ISBN number, when the book page comes up it'll show On My: Transaction Archive (or Bookshelf, or wherever the book is, like your RL).

If you type in the title, it'll also show On My Transaction Archive. Either way you'll pretty much know whether it's a book you requested or sent to someone without searching through the actual archive(s) right away.

Gail

As Sally said--the system will give you a warning if you try to order the exact copy of a book that you've already ordered.  But, be aware that if you order a different version with a different ISBN the system won't give you a warning.  This also goes for waht Gail said--it does need to be the exact version (ISBN) of the book otherwise the messages as to whether it's on your Bookshelf, Transaction Archive, etc won't show up.