There are no books about 'Clan' Maxwell as there is no 'Clan'. However two books were written to commission in the nineteenth century about the two principle lines of the Maxwell Family. The books are both by William Fraser, the first in 1863 being "The Maxwells of Pollok" and the second in 1872 being "The Book of Carlaverock" (note spelling). Both are in many ways complimentary and somewhat self seeking but give a fair outline of the fortunes of the two main lines of the Maxwell Family. It is fair to say that the histories are not totally true, there is a great deal of ommission and the genealogies are not correct especially in the early years. The book are very rare or about 100 copies of each being produced at the time. However a US company belonging to a Littleton Maxwell, 'Prince Maccus Publishing' produced reprints of both volumes in the late 1980's. I understand these are equally hard to come by. These books really only cover the histories of the Maxwells of Pollock and the Lords of Maxwell (Earls of Nithesdale), both families, which are now extinct. The history of the all the other Maxwells is wound up in the history of Scotland. There are many, many references to individual Maxwell lives in the story of Scotland and indeed a great many of them appear in all sorts of local histories. You need to read everything to understand where we all fit in. I would heartily recommend one starts with a book on the History of Scotland.