I have seen many mentions of the book, but do not own it or have access to a copy I can borrow for preview. What I have read about it is that it is quite helpful. What I am curious about is how current it is. It is sometimes deterring to follow a tutorial or use code in the documentation that is now broken due to SilverStripe improvements. With major changes in 2.4 on the horizon, how applicable will the book be?
I think quite alot of the book will still be very relavant. 2.4 does have quite a few API changes under the hood and new features which may not be covered in the book but for the most part it will still be a very helpful guide.