It contains double page spreads on 100 monsters, but they are not in alphabetical order (possibly because then that would be too much like the Encyclopedia) nor are they in order of appearance, nor are they even in order of scariness ... perhaps the order is that which author Justin Richards thought of them? There's a mix of Classic and New series creatures here too, so Zygons and Zarbi and Krynoids rub shoulders with Cassandra, the Flood and Vashta Nerada, and each entry has a couple of photographs, some slim text, and a 'Fear Factor' chart showing how scary they were.
This 'Fear Factor' seems to have been pulled from the air, bearing no basis in really how scary the things are. For example the Vashta Nerada get 9/10, while the Daleks are 10/10 ... the Werewolf (from 'Tooth and Claw' gets 8/10 as does Prisoner Zero, the Mummies (from 'Pyramids of Mars') and the Ogri (from 'The Stones of Blood') while the Haemovores get 7/10 along with Aggedor, Axons, Quarks and the Time Beetle! Maybe this is why the book is not in order of scariness - it would all fall apart!