Book Reviews vs. Literary Criticism
Book reviews are generally evaluative whereas criticism is an exploration of the ideas in a work. In other words, a book review is meant to tell you if a book is good or bad, and whether you should read it (or buy it) or not. Criticism is more of a serious analysis of some aspect of a work, whether the work be good or bad. Reviews of literary works are usually not written by scholars, while criticism is almost always written by scholars.
One of the simplest ways of distinguishing book reviews from literary criticism is the time of publication of the review/critical article compared to the original publication date of the book. Book reviews tend to be written around the time the book was published, while literary criticism will be published in later years.
Online Sources for Reviews of Newer Books
For reviews of newer (or older) books in a particular discipline, also try searching the most comprehensive journal database(s) for that discipline.
Newspapers can be great sources of book reviews from the present time and from the past.
Sources for Reviews of Older Books