The best book I have about this topic is:
Ian Buxton
"Big Gun Monitors"
>>The History of the design, construction, and operation of the Royal Navy's monitors<<
Naval Institute Press, Annapolis, MD, 1978
ISBN 0-87021-104-8
Just checked, there is a 2nd edition, which I don't have.
The author discusses the changes to the 2nd Edition. in the link below.
Naval Institute Press; 2nd REV and Expanded ed. edition (August 1, 2008)
Language : English
Hardcover : 256 pages
ISBN-10 : 1591140455
ISBN-13 : 978-1591140450
https://www.google.de/books/edition/Big_Gun_Monitors/ymGCAwAAQBAJ?hl=en&gbpv=1&pg=PT5&printsec=frontcover
Has Index and part of the book.
Cheers
Leo