I think Cartledge hits the nail on the head when it comes to why there are so many divergent views of Alexander. The book essentially comes to the conclusion that the Alexander myth is as much of a “history” of Alexander as what Alexander actually did during his lifetime. Nearly half of the book examines how the myths of Alexander developed throughout history after Alexander died – including ‘Alexander Romance’ and how Alexander was viewed during the medieval times and by Christianity as well as the continually evolving (or revolving) views about Alexander’s character and his accomplishments.Paul Cartledge wrote:
Every student has an Alexander of her or his own. Just to canvass in outline the views of some of the leading scholars of the past century, we have had Ulrich Wilcken’s reasonable Alexander, the gentlemanly and visionary Alexander of W.W. Tarn, the titanic and Fuhrer-like Alexander of Fritz Schachermeyr, the Homerically heroic Alexander of Robin Lane Fox, and the amoral and ruthlessly pragmatic Alexander of Ernst Badian and Brian Bosworth.
There are three main reasons for this enormous diversity. The first is common to pretty much all historiography or biography: we – whether ‘we’ are formally paid-up historians or not – make the past in our own image, and all history is, up to a point, contemporary history, in the sense that present concerns and our own self-image inevitably condition or at any rate colour our perception and representation of past figures.
Second, there is the specific character of the extant written evidence for Alexander: though ample in quantity, it is poor in historical quality, being mostly non-contemporary and partial in both senses (both incomplete and biased). So far as its dating goes, it is as if, one historian has written, we had to try to recover the history of Tudor England (sixteenth century) only from the essays of T.B. Macaulay (nineteenth century) and the histories of the philosopher David Hume (eighteenth century). So far as the bias is concerned, it is one of the paradoxes of history (and historiography) that this king, who took unusual trouble to secure the preservation of his own desired point of view, should have been handed down finally in history as an enigma.
Which in turn leads to the third reason for the diversity of modern estimates of Alexander: so stupendously mind-boggling were his achievements, however one glosses them morally or in any other way, that we historians inevitably interpret the great drama of his life and career in terms of our own – relatively puny – dreams and experience.
Having read 30+ books about Alexander (mostly the most recent ones published that I could find), it really does seem that every author has his or her opinions about who Alexander was and what the meanings of his accomplishments were (are). It’s as though they’re all writing book reports based on their readings of the ancient sources. From the scathing observations of Badian, Bosworth, Worthington and Prevas to the virtual hero-worship of Tarn, Fuller, Hammond, Renault, and Rogers and everything in various shades of the in-between represented by Green, Fox, and Cartledge, etc., I’ve come to see that these books are almost as much about the authors as it’s about Alexander. We may think that our own individual views about Alexander are “right”, but we really just don’t know what really happened and what Alexander was thinking. And I guess that’s just how it shall always be. It's what makes Alexander "fun" as a figure to ponder.
I saw the trailer about this new movie about Queen Elizabeth I that will hit the theaters in November. It looked very interesting and I definitely plan to check it out. So I started doing some basic research into her on the web. Right away, I started seeing divergent views on her by historians and this is only 400 or so years ago with tons of documentation available. I am a music freak (actually much more into it than history as I work in the music industry) and one of my passions has always been the life and career of the 19th century German opera composer Richard Wagner. I've read more about Wagner than Alexander or anyone else. The same applies for him; I'd say even more so than Alexander as he was a very controversial figure and remains so to this day - for example, his operas are banned from performance in Israel because he was a virulent anti-Semite and he was virtually worshipped by Hitler. But Wagner was undoubtedly one of the greatest creative geniuses of all time and his works remain as loved as ever... It seems such is the nature of history.
It may be the most balanced biography of Alexander that you've ever read, but as you're comparing the views of one modern writer with another it doesn't necessarily follow that it is the most accurate assessment of Alexander. I think you would have to first read all the sources to properly form an opinion of whether Cartledge's stance is justified. 