How to Think When You Draw is an instructional artbook series from Lorenzo Etherington. There are two volumes currently and they are packed with tips and techniques on drawing. The style is towards comics or manga but the drawing techniques are pretty universal.
These books are unfortunately only available through Kickstarter so you have to follow Etherington on Twitter, Instagram, the blog so see when the books will be re-released again. The Etherington brothers have launched multiple Kickstarter campaigns over the years and have raised £1 million for all their books so far. That's a testament to the quality of their content and books.
Another way to get alerted when new books are available is to join the mailing list. Just email "Add me, Lorenzo!" to email@example.com
Here are some pages from the two books that were sent to me.