Mostly I'm happy to work with people's RCs, but I really think the onus should be on the requester to be responsible for ordering the book they wish to receive if at all possible.  I know it's difficult as sometimes the trade & mmpb have the same isbn, but if it clearly states that the book is a mmpb perhaps it shouldn't have been ordered at all!  As everyone down the FIFO line will have to turn it down, too.

Catherine...PBS most often just lists a book as "Paperback" and if a book shares an ISBN (Trade size and MMPB size) then both can be posted to a listing that just says "Paperback" and the person requesting would not know which book you have.

To give you an idea a Trade paperback is usually around H = 8.5" x W = 5.5" whereas a MMPB is usually the size of a Harlequin Romance book (sorry don't have the measurement).

As to the OP, sometimes when ordering a book it is easy to overlook that it lists it as a MMPB when you see something you like and are excited about ordering it.  Oops, happen!!

Well done that the requester didn't restate 'the golden rule' at length (as some RC's do).  Unfortunate he requested a book specificially designated MMPB, then RC's not to send that size of book.  Good choice to decline.

I think I may have declined from the same person at some point.  Interesting thing is that the MMPB they were trying to order was a kid's book from the early 80's that never was printed as a trade size, so they are never going to get the book they ordered because it doesn't exist.  I wrote that on the decline reason too.

Don't spend time thinking about RC's, or for even spend time reading them.  Life is too short to mess with picky people.  I just respond to all of them as NOT MEETING CONDITIONS, and wait for the next person who wants the book. 

To me, it sounds like the person is expecting some people to just send the book, then they would have grounds to complain for their conditions not met. So they would get to keep the book and their credit back.

I think of mass market paperbacks as the kind you find in supermarket check-out stands and airports.  Trade paperbacks are larger.

Just for a bit of extra explanation:  mass market paperbacks are generally 7" x 4" size; trade paperbacks are generally larger, at least 8" x 5".  There are other differences (paper quality and other factors) but size is the easiest determining factor.  A PBS listing generally will only designate "Paperback" binding and not differentiate, so it is up to the Requestor to do the ISBN research for what they want and specify what they want via RCs if they want only one specific type of book.