The Malware Analysts Cookbook has some great information, I have been working through it but took a break to learn some python. But the book does go over a number of tools you can use for various aspects of Malware analysis including some reverse engineering tools. It does help a bit I suppose if you can reverse engineer so you can utilize some of the bad guys tools to your advantage but to be successful at RE, you may have to stick full time to it and ignore the pen testing.
I think to be successful at Penetration Testing, you need to have some decent background in a number of areas. So having a bit of background in malware analysis could lead to understanding how to utilize some of your pentesting tools better.