IDA Pro
Since this book tries to focus on the anatomy of the ELF format, and the concepts behind analysis and patching techniques, we are less focused on which of the fancy tools to use. The very famous IDA Pro software has a well-deserved reputation. It is hands down the best disassembler and decompiler available to the public. It is expensive though, and unless you can afford a license, you may have settle for something a little less effective, such as Hopper. IDA Pro is quite complicated and requires an entire book unto itself, but in order to properly understand and use IDA Pro for ELF binaries, it is good to first understand the concepts taught in this book, which can then be applied when using IDA pro to reverse-engineer software.