I have this book. I found it to be very unnecessary in my leetcode journey. What worked for me is repetition. It’s mostly just pattern matching. I got into three faangs recently so my strategy worked for me.
I recommend coming up with templates for the finite amount of problems.
Recursive Graph/Tree Linked List Array
The array problems can be the most unique, which means a template isn’t always possible.
Practice timing yourself. This is harder than it looks.
Stop problems that take you too long or they’ll wear you out. Come back and solve them again.