Hi @Shaz51's hubby. Nice to (sort of) meet you
You have my sympathy in trying to read the book. From my point of view CBT can be very helpful in managing depression and anxiety. But it can be hard to absorb that from a book. Perhaps just focus on the exercises rather than reading too much introductory text. If they don't make sense you can back track a little until you get it.
Alternatively there are online interactive courses you can do where the information is chunked down nicely and might hold your interest better. You can try MoodGYM here which is free.
Whatever route you take I think it'll be worth it. You'll get some strategies to help keep you calm and in a better frame of mind.
Let us know how you go 