Reviewing books is not a particularly well-paid form of journalism and it takes time. A book of any more ambition than a thriller can't be read for review at a rate of more than 40, or at most 60, pages an hour. Some books are only 120-pages long and can comfortably be digested in a couple of hours. Others, though, are 400, or 600 pages, or, in some dreadful instances, even more, and they can easily take days to get through.