First, let me say that this is a huge book. At 250 pages, you are really getting your money's worth. The town info is great, lots of useful characters, and the scenarios are excellent. I do have some complaints - the layout is more primitive than the other books, especially the neighborhood maps. On the other end of the scale, all the portraits are computer generated. First, it looks pretty hokey (maybe CGI was not as good back then?); second, the facial proportions are wrong for many of the people. This isn't a big deal for, say, Dunwich, but Arkham is somewhat repesctable and misproportioned faces just clashes with the attempted realism of CGI.
The standard layout of these books is to have a story by HPL featuring the town, to discuss town history, to break down the town into neighborhoods and show each one in detail, and then to have scenarios.
The opening story is "Dreams in the Witch House", which is probably the best available. I really like opening these books with a story by HPL - it is a reminder of how the whole thing got started. The neighborhoods take up a lot of space and describe a great many people, places, and things to meet in Arkham. I wish they would have spent some time talking about architecture in the town history section - I still don't know the difference between "gable" and "gambrel". Some real problems: street names are not clearly marked on the neighborhood maps, even when they are referred to. The combined map is not reprinted in the neighborhood section, nor is each neighborhood map shown as one piece; we only see fragments at a time. I think the Kingsport sourcebook does this best, so I assume that the layout people were still pefecting their craft at this early stage. As always, the town directory is helpful considering especially that there are so many entries that an index is needed to quickly find anything. All of the scenarios are great, although one ("the Hills Rise Wild") really would have been better in the Dunwich book, which was short on good scenarios.
Also included is a tear-out map of Arkham on very nice paper, and an issue of THE ARKHAM ADVERTISER, which also becomes a handout.
In all, this is a very informative sourcebook, with plenty of people, places, and things for investigators to explore. The only drawback, besides the poor maps, is that the spooky atmosphere was not convreyed very well. Reading the other sourcebooks, I definitely felt the atmosphere; Arkham didn't do that for me. It could have been better, but was still great.