I very much recommend the earlier part of this book. It provides a clear, concise summary of the basis of Alexander's army, the background history and the opening moves of his Asian campaign. This is the aim of Osprey books, to provide a solid basis on which to build further study.
For example:
The extaktoi may have doubled as the 1 servant permitted to each dekas...the tactical unit of the infantry was the dekas (file of ten men) which ... expanded to 16 well before Alexander's reign. Sixteen such files (16 x16) formed a lochus (later known as a syntagma) of 256 men, under the command of a lochagos. Thus the strength of the taxis was probably six lochoi (1,536 men) and that of a chiliarchy was four lochoi (1,024 men). Half a chiliarchy would be a pentakosiarchy (512 men). The size of the lochos made the relaying of commands more difficult...., it became necessary to add supernumeraries or ektaktoi.
The general who served as the taxiarches was almost certainly stationed nehind the taxis and on horseback, from which position he sent orders to the various ektaktoi whose job it was to distribute the orders. Each taxis of pezhetairoi (1,536 men) would thus have had 30 supernumeraries.
I learnt quite a bit through this book, for example, that Alexander left behind the Greek allied and mercenary infantry before marching towards the Granicus. He took all the available cavalry as he needed them to counteract the Persian cavalry superior numbers, but he perhaps didn't trust the non-Macedonian infantry. He knew he could depend upon the Macedonian infantry to stand firm in difficult circumstances, but the others were of a lesser known ability and loyalty. Plus leaving them behind meant a defence force to fall back on in the event of defeat. The description of the Granicus battle I found very useful, but Issus and Gaugamela are more sketchily treated.
However, the whole period from Persepolis to the Hydaspes is very much skimmed over. All in all though, I think the book does its function and provides a useful foundation course.