By far the most difficult part is getting the pages in the right order (it's always a good idea to put page numbers on). When I first started, I bound a book with blank pages. Now I use that one to work out which page goes where.
I use photoshop to design each page and then print a dummy copy for proof reading, before making a batch.
It didn't take long to explain that, but it takes a long long time to do it.
All worth it, if you want to make a pretty book.