I got a new art book the other day! Sketching People by Lynne Chapman - it was recommended by my Sketchbook Skool teacher, France Belleville van Stone.
I haven't read the entire book yet, but I've gotten through about 2/3 of it and I have been loving it! Lynne gives some great tips on capturing people while urban sketching and some ideas of interesting tools like Koh-I-Noor's Magic pencils. Very fun and helpful!