My current schedule involves working on 4+ HA projects in parallel.
I was looking for a book that covers open source cluster technology from a wide point of view (not just heartbeat). So, what I like about the book is the balance between the contents quantity and quality.
While its trying to cover a lot of ground it gives the reader a solid base for understanding system design, system architecture and the software technology involved with it.
(network bonding, Heartbeat, LVS, Piranha, pound, DNS ...)
The book is remarkable hands-on and shows the authors experience. It has many system schemes included, which makes understanding and discussions easy to follow up.
Highly recommended !!