Bill Clinton’s new book, “Back to Work,” is really several books in one slender volume. It’s a lucid one-man rebuttal of the Tea Party’s anti-government agenda. A series of shrewd talking points for Democrats trying to hold on to the White House and battling for control of Congress in the midst of a sour economy and growing voter discontent. A self-serving reminder of the prosperity the country enjoyed during Mr. Clinton’s tenure in the White House, meant to burnish his legacy. And a practical set of proposals — some borrowed and some new, some innovative and some highly sketchy — for restoring economic growth and creating jobs.