It's a neat book, but i was a bit disappointed. The "how they worked" part mostly can be reduced to two or three sentences like:
He used watercolours, as well as gouache and occasionally tried his hands on other mediums.
He used photographs as reference.
His wife was modelling for him a lot.

Only on rare occasions i found some more in depth information in the book.

A nice read though and i never heard of Saul Tepper before, so it wasn't a complete waste of money.