Because this textbook is online it’s easy for us to update it. Please use this form for any form of feedback, from tiny obvious suggestions to broad observations. We love getting positive feedback too (and it helps us to get support for this work). If you have more than one item to make a suggestion about, it’s a little easier for us if you fill out a form for each one so we can prioritise them. If you need to send a file (such as a screen capture) then please email it to email@example.com.