[scottjl]

one thing with ebooks is that a "page" isn't fixed any more. most reader software, if you change the font size, it will change the number of pages in a book. larger font = more pages, smaller font = less pages.

if you're playing around with font size that could cause you to jump around your place in a book. depending on the software you're using. i don't remember what kindle does, i haven't used it much.

other than that, i'm out of ideas. it might be that the books are somehow formatted poorly and kindle can't save a place or a bookmark in them correctly. report them to amazon, or post in the particular book's review section and see if anyone else is reporting the same issue. as you said, it's only 2 out of your 4 books, so i'm thinking it's more with the book files.