Project Gutenberg (A library of over 60,000 free eBooks, primarily older works out of copyright. Not a tracking site, but a source of free reading material.)
Goodreads (While personal tracking requires registration, you can browse public book pages, read reviews, and see lists without logging in.)
Book Review Sites (Free & No Registration for Browse)
Reactor Magazine (Your favorite! Excellent for sci-fi, fantasy, horror, and broader genre media criticism.)
Literary Hub (LitHub) (A great aggregator of literary news, essays, excerpts, and criticism from various sources, often including book discussions.)
Kirkus Reviews (Offers professional, unbiased reviews of a wide range of new and forthcoming books.)
Publishers Weekly (Covers the publishing industry, including extensive book reviews across genres.)