I sent two books out today and it didn't cost me any more than if I had just sent one. Is that normal?

I sent the package media mail, do they go by weight or just a stanard price?

Yes, it's normal.

Media mail is priced by weight, and the first pound is the most expensive.  It then goes up in price in increments from there.

The prices can be found here.

Thank you for your reply. So it really can be cheaper to mail more books together.

Yes, and the more you send together, the less expensive it is per book.  That is one of the big advantages of the BOB program.

That's why I'm almost always doing 3 books for one credit on my shelf.  3 books are still under 1lb and I can still fit them in a blue drop box so it doesn't cost me more to send them.  Plus, I have a lot of books to get rid of!

I sent mine out today three books cost 2.53 because they were just a little over a pound but still it was a good price.

I sent about 50 paperbacks to a friend recently and it only cost about $6 mm. 

I think after the 1st (expensive) pound, it is $0.35 for each additional.  I send hardbacks so I find it much less expensive to make my bookshelf 3 for 2.  That's why the thread re: credits for $1.50 was kinda funny to everyone on the other forum!  (she really did want to give only $1.50!)