CCNP Sec covers a lot more than just ASAs and VPN. 802.1x, securing routing protocols, securing spanning tree and VLANs, securing the data plane and control plane, protecting against IP spoofing, dhcp snooping, VLAN hopping, Mac spoofing, SSH, SNMP, configuring VPNs, firewalls, and IPS on routers, PKI, TACACS+, on top of being able to configure all the routing and switching that founds found on the R&S exam.
And there's more than just DMVPNs FYI. There's GET VPN, IPSec, EZVPN, SSL VPN, VTI, and probably some others I'm probably forgetting.
I used the Cisco Press books when studying and they were really good. I had a lot of fun studying for the exam, but I enjoy being in Info Sec and I'm a fukkin nerd
My plan was get a dual CCIE in R&S and Security since there's about an 80% overlap. But Cisco changed the exam blueprint for the security tract when I was studying and added a shyt ton of new shyt to the requirements. I was maybe 2-3 months away from taking the lab when they updated to v4 and it completely fukked my schedule up as I had to wait to see all the new iOS and hardware requirements and shyt, not to mention trying to find study materials