I'm a little baffled why other reviews are so down on this booklet, it is exactly what's described in the product description the booklet to accompany the talk given by the late Mr Sale when he would speak about his work on Colossus.
It gives a brief coverage of what Colossus does, i.e. help break the Lorenz code with the logic worked out. The text also explains how a Lorenz was later captured and it gives an insight of the technique brief enough for every listener to grasp the concept and with hints to allow any avid reader to follow up and read other texts.
Its a fine little booklet. Including a few nice black & white images of the machines involved.
If you are looking for in depth information about Colossus, their usage, or how the rebuild was carried out THIS IS NOT THE RIGHT PLACE TO LOOK! However, if you had to cover the early creation of British Computing, or dispute with the US readership about "who created the computer" then this booklet would arm you with just enough information to get by.
I have checked the references made, the text is self contained and correct in its content. It is a sweet, nice legacy for Mr Sale to leave about his work, self-deprecating to the last.
So why have I left off one star? Why not the full five of Five?... Well, Mr Sale wrote this booklet and updated it several times in his life, this impression leaves off in 1996, it could have perhaps done with an updated chapter covering the installation of the Colossus and the new aspects of the information released about the breaking of Fish with Tunny as of 2009. E.g. pointed the reader to the BBC documentary on the topic perhaps? However, it did not do this and so loses that one star as it is dated. But wholly worth the price for a copy.