Yes. Out of all the retailers, Apple (iTunes / iBookstore) has quality standards far above all the other bookstores. This includes overall quality of the content, accurate metadata submitted, cover art, and images inside the book. Let's look at these one at a time:
Quality of Content
If you have a "book" that is actually a couple of blog posts, Apple most likely will not accept this. There is a subjective criteria, so while one collection of blog posts will be fine as a book, another may not.
This includes book title, subtitle, description, etc. We double check all this when you submit the book to us, and may tweak some of this to make it acceptable—like take out any contact information that appears in your book description. So you should not have to worry about this part.
Cover art must be large, it must be a very clear image, no border, no prices, no small text, and no reason for Apple to reject it. We check this as well on submission and we will notify you if we think there might be a problem with your cover art. Apple does reject many books because of "blurry" cover images (but not the ones we create, of course :)
Images Inside the Book
Out of all the books that Apple rejects, this is the #1 reason. Sometimes, there is no way around this. Apple is extremely picky on the level of quality of images inside the book—specifically that all text in the images is clear and readable. Sometimes, this is not possible given that book images may be multi-page, or usually very large with small text. When these images are reduced to fit in the book, the text is just too small to read.
Here is an example of the image that caused this book to be rejected:
Bo Bennett, PhD
Social Scientist, Business Consultant
About My Businesses > http://www.archieboy.com
About Me > http://www.bobennett.com
Books I’ve Written > https://tinyurl.com/bosbooks
Courses I Teach > https://tinyurl.com/boscourses
Podcasts I Host > https://tinyurl.com/bospodcasts