Reddit mentions of Cisco ASA: All-in-One Firewall, IPS, Anti-X, and VPN Adaptive Security Appliance (2nd Edition)

Yeah and the 5520 is getting up there in terms of its abilities. So if you really need something that big I'm guessing you have a pretty large network and potentially complex requirements.

And not to be too blunt but that's also determined by your abilities and understanding of what a firewall should do in the first place. You can do some basic stuff with a simple outside-inside-management scheme, but with a network as potentially large as yours you will (should) have management networks, security networks, DMZd networks, Server networks, MPLS networks, VPN networks, etc., and subinterfaces for dealing with all the security requirements thereof.

But you can try this book for reference. It's pretty good through software 8.2.

Someone else pointed out though that the software versions > 8.2 change things quite a bit. So if you're starting from scratch you may want to upgrade to 8.4 (if it doesn't come with it) so you're ahead of the curve.

Or perhaps downgrade to 8.2 (if needed) since most people are familiar with that version and priors. Also Cisco is good about update their software trains, so 8.2 will continue to be supported for some time (patches, security patches, etc.)

Good luck!