Good books about the internals of Rails 3

Hi, I'm a new RoR and Ruby developer and I'm searching for some good
resources (books or website) that go a little further than books like
the railstutorial (which is excellent btw).

But after reading this, I feel like as long as I'm working with
scaffolding and simple gems, it's ok, and a lot can be accomplished with
this but I would like to have a deeper understanding of Rails behavior
and not being lost in the magic.

I recommend these two:

http://www.amazon.com/Crafting-Rails-Applications-Development-Programmers/dp/1934356735/ref=sr_1_1?ie=UTF8&qid=1348172437&sr=8-1&keywords=crafting+rails+applications

http://www.amazon.com/Rails-Edition-Addison-Wesley-Professional-Series/dp/0321601661/ref=sr_1_2?ie=UTF8&qid=1348172437&sr=8-2&keywords=crafting+rails+applications

Metaprogramming Ruby

Do you think it's still reasonable to buy those books, knowing that RoR4
will be released soon? I'm especially interested in Crafting Rails
Applications, but I don't want to buy something that will be obsolete in a
couple of months.

Why did you buy a PC?

@Norbert Thanks for the constructive answer! I’m glad you noticed that there is no difference between using two-year-old PC and two-year-outdated web framework!

More seriously: changes between RoR2 and RoR3 were quite significant, so buying a book about RoR2 internals to use it with Rails3 was rather a bad idea. I’m trying to learn if it’s the same in this case.

@Norbert Thanks for the constructive answer! I'm glad you noticed that
there is no difference between using two-year-old PC and two-year-outdated
web framework!

More seriously: changes between RoR2 and RoR3 were quite significant, so
buying a book about RoR2 internals to use it with Rails3 was rather a bad
idea. I'm trying to learn if it's the same in this case.

I suggest you weigh at the pros and cons. If you can wait for a couple of
months for the release of rails 4
and another or 2 for a good book, then I'd say wait. But in those months,
you could've already acquired a
good deal of knowledge when you buy a rails 3 book. There are some new
stuff going out in rails 4 like
turbolinks, doll caching and strong parameters, all of which are kind of an
upgrade to the version that rails
3 is using so you might want to look at how those work at the moment while
waiting for rails 4.