Sometimes called "the French Goodreads", Babelio is both a database of literature and a social network that allows users to keep track of and review books they have read. It also contains excerpts from and links to professional reviews in a variety of general media publications (e.g. Le Monde, L'Express).
Finding reviews of contemporary French novels
Reviews of contemporary books can be found in a variety of different publications, including:
broad, general interest newspapers and magazines (Le Monde, Libération, Le Figaro, L'Express),
general audience magazines focused on cultural or literary topics (Les Inrockuptibles, Lire, etc.),
literary journals or reviews that are aimed at a more academic or intellectual audience (Quinzaines, Nouvelle Revue Françaises, etc.)