This book has earned some well-deserved praise for its even-handedness. The author, Matthew Continetti, is a contributing editor at National Review; his Wikipedia page will tell you that he was previously at the Weekly Standard. He has a gig at the American Enterprise Institute. Conservatives, he is calling from inside the house.
Continetti tells a pretty standard story of conservatism's rocky road since 1920 and Harding/Coolidge. He takes a look at the ups (e.g., Reagan) and downs (e.g., Taft, Hoover, …) of conservative fortunes in the GOP and in American politics. It's also a 40,000-foot view of American history over the past century, stories that have to be told in order to make sense out of the politics. There are also a lot of thumbnail sketches of (mostly) conservative journalists and political philosophers over the time period. And their associated institutions.
One downside: it's a fast trip, and the coverage is necessarily superficial. But an overriding theme is the stresses and strains between different flavors of conservatism. There's neos, paleos, free-marketers, populists, … And, unfortunately, some folks who could be described as racists, anti-semites, grifters, conspiracy theorists, and even some lunatics. It would have been easy to neglect the various ugly spots in conservatism's history, but Continetti does not.
Fun fact: Continetti was born a few months after Ronald Reagan's first inauguration. So he's telling a lot of these stories second-hand at best. Given his youth, he does a fine job.
Something I didn't know: National Review's publisher, Bill Rusher, was livid when Bill Buckley hired George F. Will to write a column for the magazine; he campaigned to have Will fired. And usual writer Stan Evans quit rather than to work at the same magazine as Will. Will's problem: he saw through Nixon, and wrote the truth.