I gather you mean flipbooks like these, showflipbook.com/examples.php for example, showflipbook.com/examples/5d5de346b7/view_book.html - they look attractive, but the 1st question surely should be, do they have learning value?
At first glance (and I'm not a Flash expert) they don't look accessible themselves. However, if you can provide links to (an) alternative format (ideally HTML, or Word doc, PDF etc.) then that is probably OK. The book above has a "View PDF" link - note a link like this should be on the Web page as well, not just in Flash, for example (put as much detail as possible in the links), HTML:
<li><a href="http://showflipbook.com/examples/5d5de346b7/view_book.html">[Title] - Flash flipbook</a></li>
<li><a href="http://showflipbook.com/examples/5d5de346b7/Tanzania_-_Thesis_Zachariah.pdf">[Title] - PDF alternative (1.3 MB)</a></li>
The only definitive way is to test with assistive technologies, and ideally real users. I hope that helps. Nick
I tested last year probably 5-10 different flip books and have this one still available as an example how normal book of moodle (by Petr) can be changed to flip book. In addition to what Nick said I guess accessibility of flipbooks depends also on the method how you create them. For "normal users" typical flash flip books are cool and easy to use but you might want to use different kind of elements for visually impaired learners. As far as I can remember some of the first (commercial) flip books were developed exactly for kids special education - some products like http://microsite.leapfrog.com/tag_qe/demo.html
I haven't seen those flipbooks developed by a Moodle Partner but I guess they must be rather similar as these demos that Nick and I gave.
The flip book used by you is cool...
Which activity module are you using? I want to deploy on my site too. thanks.