The first time I noticed Shadowhouse, I was walking down Hawthorne St. and saw the books in their window. Pulp novels and old occult texts -- including a collection of Austin Osman Spare's writing that is very hard to come by. I made a note of the place and that I would definitely want to come back later.
I have, more than once, and this shop continues to amaze and delight. I bought a hat there which I'm wearing to my wedding, and they have a great selection of fine art, kitsch, esoterica, and collectibles, with an emphasis on strange books. They stock hard-to-find ritual herbs, unique clothing, and Cthulhu statuettes.
You know that book you read when you were a kid? The plot is ubiquitous -- kid goes to a weird little shop, buys an oddly colored statuette, and when they goes home it starts talking to them? This is the shop where you buy that item. It's an absolutely wonderful and irreplaceable treasure of Portland, and is one of the reasons I like to live in this city.