I've read two impressive chapbooks recently: Chalk by Pat Cadigan (part of the This Is Horror series) and Terry Grimwood's Soul Masque from Spectral Press.
Despite being roughly the same length and both being 'horror' the two were as different as, well, Chalk and cheese. (Sorry.) Chalk starts off quietly and realistically, building up a view of the narrator's world - it's a growing up story, and tells of two girls who are best friends, and who mark their surroundings with chalk to indicate good places to hide from parents and siblings. The weird element intrudes gradually, and is subtly done - just how much should we believe of what the narrator is telling us, looking back as she is at events she can surely not have fully comprehended at the time? It's ultimately a story about the loss of the past, of the fragility of memory, and of childhood innocence so close you think you can recapture it...
By contrast Soul Masque starts with a bang; in fact it starts with an epilogue and ends with a prologue. It's a noir-ish story about shifting allegiances in the battle between Heaven and Hell, it's action driven by a cast of drug-addicts, angelic singers, and hideous demons. There's a lot of skill in the way Grimwood packs in so much unobtrusive world-building; equally so in daring to use a few different narrators in such a a short format. In contrast to Chalk's elegiac, quiet tone, Soul Masque seems to race along, driven by staccato prose and vivid one-line imagery that hit you where it hurts.
So, two excellent but very different chapbooks. Take your pick or just read both. And sorry again about that chalk and cheese joke.