I did a deal in the book bazaar last week, 2 for 1.  Today I received my books.  They were wrapped in a brown lunch bag and sealed with scotch tape.  One end of the package was open and if it got ripped a little more, the books would have fell out.  The pages are wavy on both the books.  Do I let them sit in my house for a few hours and see if they are wavy because of the difference in temperature before I mark them received??  How can I tell if it is really water damage???

Water damage pages will feel different - slightly crunchy and thicker than non-damaged pages.  You might also be able to see a water stain line between the damaged part and non-damaged part of the pages.

The more I look at them and feel them I think they got a little wet in transit.  After reading the help docs more I think I should mark this received with problem.

If it's really water damage, there will be more to see than just wavy pages (you'll see some staining if you look closely).  It seems that much cheaper paper is being used in books now and even brand-spanking new books can have wavy pages.

If they are only wavy from humidity, you can try placing them flat with something heavy on top of them.  I have done this with books that I got on really rainy or humid days when the book wasn't plastic wrapped - the book wasn't wet, but had sucked up a lot of moisture.  Sometimes just letting them get rid of that humidity with the weight will straighten the pages back out.