I appreciate the effort that went into this book, but as someone who is learning philosophy casually, this book is just too academic for me. If you are someone who's studying philosophy at university, I'm sure you can make more use of this book than I could.
One thing that's interesting is that this book doesn't follow a sequence, it's divided into five parts but the first two chapters talk about 18-20th-century humanism, the next two chapters talk about the origins of it, and the last chapter is about modern humanism. The author mentions at the beginning that you can read in any order you want, but it just seems... unnecessary.
Not a bad book by any means (it simply means that I'm the stupid one), but if you're a casual like me, you'd probably be better off reading the original works of humanist writers such as Erasmus and Moore than starting with this book straight away.