I actually bought the first edition of this book and loved it (but not EF at the time). When I saw a new updated edition for EF4 I jumped at the opportunity to learn the new and improved features.
The book starts with excellent introductions to all the different ways to query and so on and doesn't assume a huge knowledge, although I think it helped that I understood LINQ and SQL already.
I bought this book electronically and have been reading it on my Kindle, I bought the paper edition originally and decided my back needed a break!
I am only about 60% of the way through the book but am very impressed with the detail and descriptions provided.
The downloads available for the book are easy to find via the books website as well as providing details about events by Julie. I am disappointed that I missed out on registration for DDD Modern .NET day at Reading, UK where Julie is talking as the event sold out so quickly.
I found that the number of diagrams to be fine, there are just enough to help explain and when using it on a Kindle they appear fine and readable.
As for the reviewer who is angry at purchasing the wrong edition, well that's not Amazons fault or Julies.