And if I may judge from the reviews, many of these books are well and carefully written; much thought has gone to their composition; to some even has been given the anxious labour of a lifetime.

如果我能根据书评下断语的话，很多书是作者呕心沥血的结晶，作者为它绞尽了脑汁，有的甚至是孜孜终生的成果。