Amazon books and Google books. They let me read snippets. I like reading the first few pages; they tell me whether the author can write; it's important to know.
Go to Amazon and:
Read the first paragraph of Places in the Dark by Thomas H Cook.
Read the first six pages of Kiss Me, Judas by Will Christopher Baer.
The first paragraph of The Big Sleep by Raymond Chandler (utterly brilliant - you could sustain an academic thesis on it).
First page of Angels Flight by Michael Connelly (the always reliable Connelly).
And for comparison:
The first few pages of To Kill a Mockingbird. You'll have to scan down for a searchable edition. The real writing begins about five pages in with "Maycomb was an old town, but it was a tired old town when I first knew it." Shame on Harper Lee for those first pages (heresy!).
Google has the first few pages of The Great Gatsby. Shame on Scott Fitzgerald (even more heresy!) for those first few pages.
Surely an amusing diversion, but also something useful. Raymond Chandler set the hook in the first paragraph. (How good is that!) He introduced his character, established a voice, and made us wonder why a fabulously rich man wanted a private eye. I don't know about you, but I was hooked.