So far I think the retention rate is the same. Although honestly its still too early days to really know. One inconvenience I didn't think to mention, as it kind of relates to review - an actual book is easier to flick through to where you remember seeing the information you want to look at again. The Kindle is a little trickier. But probably just a matter of getting used to.

Most of my books are digital format also. They had been sitting there just waiting and being wasted. Finished over 5 books in the last 2 weeks already (as opposed to normally half a book in that time).