In the 19th and early 20th century books about clans were a result of the Victorian fascination with Scotland. Quite a few books were written about the Clan Maclean. The following books about the Clan Maclean are out of copyright and in the public domain:
A. Maclean Sinclair, The Clan Gillean, (1889)
J.P. MacLean, Renaissance of the Clan MacLean (1913)
J.P. MacLean, An account of the surname of Maclean, or Macghillean (1914)
However, recent studies by Nicholas MacLean-Bristol suggest that many of these books were based on a somewhat biased 1734 manuscript by Dr Hector Maclean. He has since written his own books and articles on the subject that are based on sources not available to the earlier authors.
For more information you can read some articles about the Clan Maclean written by clan members and others.