I just started to explore about ASA, as I needed to implement a cisco firewall for one of my projects. Fortunately, Narbik also launched Site-to-Site VPN which is sample part of his CCIE Security Workbook. I would advocate that his book is incredibly awesome because of the way he explains and the topology he designs for the labs.
Furthermore, I recommend to check the ASA specifications and models comparison at the Cisco website. It will be useful for pre-sales engineers.