After browsing the paper, it looks like the idea is to extract common sequences of letters from a given text into a table of a certain size, and then replace those substrings with references to the tables in the text.
That is how text in the Infocom text adventures is encoded when using the Z-Machine (together with some other tricks, e.g. "shift" codes for uppercase/lowercase similar to telex).
But I have no idea if the tables were created with that particular algorithm, or with a different algorithm. OTOH, the algorithm is straight-forward, so once you hit on the idea (even independently) you'd probably come up with a similar algorithm.
Edit (more details): As described in the reverse-engineered [Z-Machine standard], text is packed into three 5-bit codes per two bytes. There are "shift characters" that switch between lowercase, uppercase and punctuation alphabets (similar to shift codes in the Baudot telex encoding). There are also three special characters which together with the next 5-bit code form a reference into the dictionary, so the dictionary has a fixed maximum size of 3*32=96 entries. The dictionary entries I have seen can be frequent English words, game specific expressions, and are even used inside words.
This is literally the decoding algorithm from the paper, with three "special coding symbols" instead of the single @ used in the paper:
The decoding is performed by examining the compressed data for special coding symbols. When a special coding symbol is found the code is used to index to the appropriate string in the decoding dictionary. The string may then be substituted for the code.
To be useful, the Mayne-James algorithm needs (1) a fairly large amount of text, (2) text that has enough common substrings, (3) the need to compress text because space is more important than time, or the circumstances where decompression is needed are simple.
So text adventures are probably one of the few use-cases where this algorithm is really of use, given that the Infocom team had to port games like Zork from a PDP-10 mainframe to home-computers with limited floppy storage (which caused Zork to get split into three parts).
As Mark Williams mentioned in the comments, the Company Level 9 also used a dictionary based compression scheme in the A-Code virtual machine for their text adventures, confirming that text adventures are a prominent use case for compression. However, they use (at least in later versions) multiple dictionaries hashed on the first two letters of the word, with a "keep some letter from the previous dictionary entry" scheme, and any byte larger 0x5d seems to be an index into the "current bank" dictionary.
So that's sufficiently different from the Mayne-James decoding scheme that I would assume it was invented independently.
given that the algorithm was the state of the art for several years
Any proof for that? If you don't even know that it has been used in practice?
There have been quite a few compression schemes around well before Lempel-Ziv, which have been used frequently in many places, e.g. run-length encoding. And Huffman encoding is from 1952.
The printed book, if judged by the price, is a rarity
Some offers on Amazon for rare items have a price based on some sort of funny machine-learning algorithm; don't draw any conclusions from the price to the real value of the book.
