I sent them to my brother, who was great at cartoons, and asked if he'd illustrate them. He liked the stories and said he would. Some years later, he remembered his promise and surprised me with an envelope full of pictures.
I approached a publisher and was told that because the illustrations were in colour, the book would have been too expensive to publish. Also, because the overall number of pages wasn't great, it would have worked better in hardback than softback, which would also have upped the cost. My brother didn't want to redraw all the pictures in monochrome line and I didn't want to write more stories, so we left it as an idea to do something with ourselves when we got around to it.
We never did. The stories have been online for years (my brother died in 2009) at https://mud.co.uk/richard/sbos.htm, and there's even a copy in MUD2 that I used as a test for putting books into the game.
The sequel was going to be called The But Book of Buckets, by the way, because the vowel sound in But, Book and Buckets was the same for us but annoyingly-different to people with a southern accent.
Recently, Amazon's self-publishing arm introduced hard covers as an experiment, which reminded me of The So Book of Spoons so I put together an edition.
The stories are probably too dated in terms of their subject matter and their blunt naughtiness for anyone today to want to buy them (although they can), but that wasn't why I published it. My brother and I had the same initials, and always said we should write a book "by R A Bartle and R A Bartle"; I'm happy to say that our goal is now, finally, fulfilled.