Reviewing this book as someone who didn't have any prior exposure to ODEs.
I'm really leaning between a 3/4 star here. The book started out rough, where the first 3 paragraphs of chapter 1 were good, only to find out by other people's opinions on mathstackexchange that the other paragraphs of chapter 1 had exercises in them that are introduced way too early!
So I had to skip 3/6 paragraphs from the get go due to that.
The rest of the book was fine in that sense, though sometimes when I was reading, I couldn't help but feel as if I was reading a summary, rather than a textbook. The lack of theory is a bit too much, most of which are located in the appendices or the second to last chapter. It was very much about the formulas and knowing how to use them.
It reminds me of when I read a short collection of thoughts by Rota, in which he said that ODEs are taught the wrong way. It's almost like Calculus 2 class, with a bunch of tricks to find the solution of the ODEs, without explaining too much on why they're useful, if they even are useful in practical contexts! This book definitely falls within the class of "The old way of teaching ODEs".
That being said, the book wasn't bad, I skipped chapters 8 and 14, and am sure I will come back eventually to finish those too.