I'vejust finished proofing a book about Dover in WW1 - it actually got quite interesting as it progressed. However, it doesn't really matter what it's about, it's checking for errors and spelling and grammar mistakes, and does it make sense to you?!
It does make sense but any bits that are muddled I have pointed it out - there's load of techie bits and navy speak so some of might be factually correct. Not looking forward to proof-reading the whole thing though.
You're right, you just have to trust the author on the techie bits. Most of my corrections are usually peculiar punctuation.... when someone gets on a roll, they forget to breathe on paper!