To those of your readership who know what Latex is, it is sufficient to say that this is one of the 2 standard works on the subject and well worth reading. The other is called "The Latex Companion" and is on my list for purchasing next.
The remainder of the review is for those who have never come across Latex and should be read by aspiring engineers and scientists and by typists who want high standards of output. Conventional word processors such as those in MS Office and Libre Office are "jacks of all trades ...." and are sufficient for many uses but they are not suitable for documents with complicated formulae eg mathematical, chemical or engineering. The answer is to use TEX. This is a typesetting program but it needs too much technical expertise for mortals. However, help is at hand in the shape of Latex which is an enormous collection of mini-programs based on TEX which make life easier. Lyx is a "document processor" based on Latex but its use needs some knowledge of Latex. Whilst my requirement is for maths, I quickly came to think that Latex was OK for normal use because the resulting documents look so much better on the page. Indeed, I have heard that the secretaries in a major academic institution voluntarily switched over all of their work to Latex based documents.