Stephen Coleman is a member of the Socialist Party of Great Britain (SPGB). In this book he attempts an objective look at the SPGB's distant ideological cousin, Daniel De Leon of the U.S. Socialist Labor Party (SLP). In my opinion, Coleman is too positive to De Leon. For instance, De Leon in my opinion *did* believe in a version of the “iron law of wages”. It's also curious that Coleman downplays De Leon's differences with James Connolly, which were considerable. (The future leader of the Easter Rising was a member of the SLP during his stay in the United States.) While De Leon was contradictory (and more flexible than his successor as SLP leader, the inimitable Arnold Petersen), the man was at bottom a hopeless and muddled sectarian. Since Coleman's own party are just as hopeless, it's no big surprise that he doesn't get it.
Coleman does make two interesting observations, however. First, that De Leon's vision of a future society might have been inspired by Bellamy's utopian novel “Looking Backward”. Before becoming a Marxist, De Leon had been a “Nationalist”, i.e. a supporter of Bellamy. Second, Coleman (somewhat reluctantly) points out that De Leon's view of party organization had strong similarities with Lenin's “democratic centralism”, yet the two men apparently never met or exchanged ideas.
Otherwise, I found “Daniel De Leon” to be quite bland and too apologetic. Also, it's not really a biography, but rather an extended essay on De Leon's politics. And no, it's not about Alzheimer's disease, so Amazon's subtitle is probably a mistake! The correct name of the series is "Lives on the Left".