First, here is a link to the book:
Cameron’s commentary is meant for students more advanced than I am, advanced undergraduates in classics, and beginning graduate students. He assumes you have Smyth’s grammar handy, Liddell & Scott Abridged, as well as a good recall of the forms and syntax principles presented in a textbook like Mastronarde’s.
The commentary is more sparse than that in Geoffrey Steadman’s student commentaries, but Cameron’s comments, where they exist, are more thorough. Steadman gives at least a brief note on everything that might baffle somebody who has studied Mastranarde, but whose memory of it is shaky–somebody like me. Unfortunately Steadman has no commentary on Book I.
If you are like me, Cameron will help, and is worth using. I augment Cameron in two ways. First I use the iOS app Attikos, as a dictionary and parsing aid, then I count myself lucky if Cameron presents a comment. Secondly, I work back-and-forth from English translations to the Greek words in the text; this helps me identify idioms and secondary dictionary meanings. These methods usually get me out of trouble. When I am still baffled, I run up the distress signal here.
I also use Louise Pratt, The Essentials of Greek Grammar.