Contrary to the previous reviewer, I did not find this book "excellent", neither is it exactly on "Hellenistic warfare". The thesis is, indeed, that, at some time between 160 and 140 BC, both the Ptolemaic and the Seleucid heavy infantry abandoned Macedonian phalanx formations and sarissas and were re-organized and re-armed along Roman lines.
Oddly enough, since this is the main premice underlying the thesis, the author does not even discuss the assumption that the "Hellenistic phalanx was no match to the Roman manipular tactical system." It is taken for granted, without any further analysis, partly because the Romans won three set-piece battles - twice against the Antigonids and once against the Seleucids - against Hellenistic phalanxes and because Polybios, a pro-Roman historian, and Livy, a master Roman propagandist tell us so. Needless to say, this is a rather strange way for a historian to make a case.
The second problem is the evidence. It is very unconclusive and, in many cases, it just cannot be used to support the wild claims made by the author, even by stretching it to breaking point. This is particularly the case for the Ptolemaic evidence - a collection of tombstones, steles and pieces of pottery - from which the author concludes that the Ptolemaic heavy infantry was re-equiped, re-trained and reorganized as Roman manipules. Needless to say, this is not the only, and probably not the most likely explanation. As the author mentions, all of the infantry types that he describes look very much like thureophoroi, that is a type of medium infantry that were developed in Hellenistic states and which were more heavily equiped than traditional peltasts but more flexible than phalangites. The need for and usefulness of such troops was clearly recognized by both Antigonus Doson (at Sellasia) and by Philipoemen, strategos of the Acheans, without any need of Roman involvement or of copying the Romans.
Another point which is highly disputable is the author's tendancy to rely on wishful thinking. Everytime a half-worn tombstone or a pottery shard shows a soldier who might be wearing chain mail, Nicholas Sekunda draws the conclusion that this is further "evidence" of the hellenistic infantry reform along Roman lines. This is not exactly convincing, to put mildly, especially since mail seems to have originally been borrowed by the Romans from the Gauls. If this is the case, would't it be much more simple to believe that some of the Hellenistic kingdoms' troops borrowed it from the Galatians, that is from the Gauls which settled in Asia Minor during the third century BC, especially since some of these troops were Galatian mercenaries themselves?
The author is on (slightly) firmer ground when dealing with the Seleucids. This is because we know from the sources we have on the Daphne Parade, a military parade when Antiochos IV Epiphane showed off the might of his kingdom, that there were some 5000 troops (approximately the strength of a reinforced legion) the equiped as Roman infantry. However, this is all we know for sure, and all the rest - for instance the claim that, gradually, the whole Seleucid phalanx was so re-equipped is not supported by any kind of evidence. Although some authors (such as Bar-Kochva in his excellent study on the Seleucid Army) claims that these made up half of the Argyraspids, with the other half appearing as Chalkaspides and retaining their traditional organization and equipement (pike infantry), this is no more than an interpretation. In reality, we simply do not know if the 5000 Roman-style infantry were part of the Guard and a crack force, although this does seem very likely.
So, although the author's thesis is interesting, there is very little real evidence to back it up with. Apart from the statement that 5000 Seleucid infantry were re-equipped in Roman-style for a parad in BC 166 and that we never hear of them again, the rest of the evidence can very easily be interpreted in a quiet different, more simple and less far-fetched way than the author's interpretations. For instance, the mercenary garrison troops shown as equipped in Roman style are most likely to have been thureophoroi. These would, of course, be more suitable as garrisons that phalangites.