Alex was super-helpful to me. I had an edge-case problem using batch writes; the issue was assembling the batch in R to pass through the paws api, basically a bunch of really tricky nested lists, and I had one element out of place.

Alex answered my questions in such a way that I myself saw where the bug was in my code.

He saved me easily several hours of time.

At my hourly rate, this means that the book had a negative cost in my case.

I was able to repay the favor, I suggested an improvement to one code example in the book which Alex eagerly accepted.