On Nov. 24 I mailed a book that had been WLed by another member. I waited 3 weeks before sending that person a PM asking if the book had been received. I was PMed back that they were in the process of moving and maybe the book had not been forwarded yet. Today I got that book in the mail with 2 stickers from the Post Office on it: Notify Sender of New Address (dated Dec. 03) and another sticker partially covering the new address that says UNCLAIMED Returned to Sender. Should I PM the original requestor and oofer the book again? Should I ask for two credits since I would be out postage twice? Should I just post it again and not offer it to ariginal requestor?

I would PM the requestor and let them know that you received the book back and tell them what stickers were on it.  I recently moved and I know it was difficult to keep up on my PBS packages.  As them if they are still interested and explain that you would like to send it again but as you would be paying postage twice perhaps you can work something out.  Is there a book on their shelf that you are interested in?  Perhaps you could swap that in lieu of the second postage.  If you could think of a really polite way to ask about paying for postage, I might do it but if not, I might be inclined not to mention it and see if the requestor brings it up first.  Maybe after the conversation starts you can see where the requestor stands and maybe bring it up then.

Keep the package/wrapper for now. PM the person who was wishing for the book and politely explain what happened, and request a credit as compensation for the postage. Give the person a deadline to respond (PBS likes 7 days). If the person responds, you can negotiate what to do from here. (Perhaps the book has already been sent by someone else at this point? Or if the person gives you a credit, you can probably repost IF the member has updated the address on file.)

If there is no response, report it to R&R via the Contact Us link at the bottom of the page.

I would read the Help Center section titled:

You need to read the help section on this.
 I just had a book come back today.
 I have pm'd the person and wrote the address that printed out on the wrapper. [I did not hand write it.] 

 I said that if they would send the correct address I would resend it.

My question is can I resend it in the same package?  I used the stamp meter from the office and it does not look like it has been canceled.

This person does not have a profile, but their book list does show up so I guess they have not closed their account.

Amye said: My question is can I resend it in the same package?  I used the stamp meter from the office and it does not look like it has been canceled.

Unfortunately, no, you can't.  The meter paid for the first mailing.  This would be the same as reusing uncancelled stamps.  From the help docs:

Is it OK to reuse uncanceled postage stamps?

Jason,  be glad the post office didn't charge you the return postage!  That happened to me - I mailed a book and it was returned - and the postal worker came to my door with it and said I had to pay the postage to get it back!  It was right there in his hand - and if I didn't pay, it would probably just get destroyed :-/