If you’re familiar with Backhouse’s The Illuminated Manuscript, then you’ll understand why you want this one; it’s basically The Illuminated Manuscript on steroids. An excellent book, with plenty of high-quality pictures and details on the scribes who created them. It’s what I turn to first when I’m looking for ideas on a scroll.
If it has a failing, it’s that it’s skewed heavily towards works from the British Isles and northern European works. This is a general characteristic of Backhouse’s books, because they’re (almost?) all taken from manuscripts in the British Library.