Each volume in this series is essentially a ‘best of’ compilation of physics footnotes (including several I haven’t yet published online). The books are delivered to you in PDF format, with each page formatted as an attractive poster. This means you can print the pages out and bind them into a physical book, or laminate them individually and decorate the wall with your favorites. In addition (and a number of you asked for this!), when you’re reading a volume online as an ebook, you can click any poster to go to its corresponding web page, where I usually provide more information about the topic, often including a video or animated GIF.
If you just want to purchase a volume outright on an ad hoc basis, you can do that below. (Note: Even though the Buy Now button takes you to a PayPal page, you don’t need to have a PayPal account to purchase; just scroll down to the Pay with a Card button if you want to purchase using a credit card).