I studied Digital Animation at University and we used 3D Studio Max. I guess it all depends what you want to do once you have learnt to Animate. If you are looking for a career in Animation then again it depends what you are looking industry you are going to Animate in. I say this because although I learnt 3D Studio Max, this software is widely used for the Games Industry, while a software package like Maya is a lot more suited to the Film industry along with Softimage XSI.
I think the main thing is to get comfortable with one software package and then if you find you want to learn another, moving over is not as much of a steep learning curve. I used 3D Studio Max for my Uni work and then to get a job had to learn Maya which while it took a little time, the principles of Modelling and Animation are the same, it was just a matter of getting used to the new tools. I don't know of any ebooks that are very good but Digital Tutors have a wide array of training available and you can sign up for a free account which gives you access to a large selection of free videos to get started, then if you want to get more specific they offer paid training in specific areas. Lynda.com also offer a very good selection of training on these type of subjects
Hope this helps