Today Duncan Eppingannounced that two of books he wrote with Frank Denneman will be available in Kindle version for free between 05.06.2013 and 06.06.2013 on Amazon.

I read both books and they are really really good.

Here are links to Amazon website:

VMware vSphere 5 Clustering Technical Deepdive

VMware vSphere 4.1 HA and DRS Technical deepdive

Enjoy!