Histories and Historians
The earliest surviving histories of the clan were written in the 17th century, and some of these are available online:
"Genealogie of the Mackenzies Preceeding The Year 1661 by A Persone of Qualitie" [Sir George MacKenzie of Tarbat].
"Genealogie of Surname of Mackenzie since their coming into Scotland" collected by John Mackenzie of Applecross (1667).
"Genealogy of Most Considerable Families ... of Mackenzie ... Preeceding 1667" collected by John Mackenzie of Applecross.
"History of the Family of Mackenzie by Sir George Mackenzie, First Earl of Cromartie" [Tarbat as above - but written later].
A list of other 17th century manuscript histories that survive can be found in Andrew McKenzie's "May We Be Britons" - below *.
19th century histories and genealogies:
William Fraser, "The Earls of Cromartie" (3 Volumes, Edinburgh, 1876) - available online via www.archive.org
Alexander MacKenzie, "History of the MacKenzies" (Inverness, 1879 & 1894 - reprinted in Canada in 1998). Online here.
James D. MacKenzie of Findon, "Genealogical Tables of Clan MacKenzie" (Edinburgh, 1879) - tables & intro available from CMSSUK.
20th century books and articles:
Edmund Mackenzie, "Cabar Feidh Gu Brath: A Lay of Clan Kenneth" (Melbourne, 1907).
William Matheson, "Traditions of the Mackenzies" in Transactions of Gaelic Society of Inverness, Vol. XXXIX, (1963).
Duncan Warrand, "Some Mackenzie Pedigrees" (Inverness, 1965).
Earl of Cromartie, "A Highland History" (Berkhamstead, 1979).
21st century books and articles
Aonghus MacCoinnich, "The Emergence of Clann Choinnich c.1475-1508" in Boardman S. & Ross A. (Eds), "The Excercise of Power in Medieval Scotland" (Dublin, 2003)
Andrew McKenzie, "Clan MacKenzie and the Jacobite Risings" (London, 2011).
Andrew McKenzie, "May We Be Britons: A History of the MacKenzies" (London, 2012) * - available to buy here.
Graeme M. Mackenzie, "Cabarfeidh's Cousins: Essays in Clan MacKenzie History and Genealogy" (Inverness, 2015).
The most complete bibliography of manuscripts, books, and articles, about Clan MacKenzie can be found in "May We Be Britons" *.