I have only ever read The Rights of Man many years ago. I loved Paine's wit (there are many classic one-liners, including my favourite anti-monarchist barb of all time: "a hereditary monarch makes as much sense as a hereditary poet laureate") but found his philosophy superficial, probably because I had just left grad school.
This biography makes a compelling case for Paine being one of the greats of the enlightenment - man able to combine philosophical ideas with prose that was intelligible to the masses and who wrote about any number of topics (and even designed bridges!). In this version, Paine is an important figure worthy of serious study and as important (if not more so) as his contemporaries, with contributions to both philosophy and actual political life (including helping to draft multiple constitutions).
I have two nitpicks with the book.
The first is that Nelson loves Paine too much. He asks us to forgive Paine's faults, after all Paine is only a man. But Nelson does not extend the same courtesy to some the people who argued with Paine, particularly John Adams (who comes across as an absolutely awful person in this book) and Edmund Burke (whose position on the French Revolution is considered some kind of betrayal, both personal and political).
The second major issue is with Nelson's portrayal of Pitt the Younger's "terror." Nelson equates the suppression of free speech in England (something that was quite common at the time) with the Terror in France. I am nearly a free speech absolutist, but one cannot claim that jailing people for months for writing things is in any way the same as the mass murder of thousands of people. This is just absurd and downright preposterous. I really don't understand where Nelson is coming from here.
But those two things aside, this is a really interesting biography of one of the most important writers of his era.
Well worth your time.