They were the odd couple of cinema: Hitchcock's spry, intelligent thrillers were very much at odds with Selznick's adaptions notable for their fidelity to their source. Hitchcock, in contrast, was anything but faithful to the source material of his many film adaptions. Both adaptions and original material focused on key visual images around which the plot was built. Selznick was the opposite of Hitch in that his productions were focused more on the narrative. Their collaboration managed to enrich each other's skills.
Although they made few films together during their ten year "collaboration" (in reality Hitch was under contract so his status was more as suborindate than equal), most of them are hampered by their lack of cohesive styles. As producer/director they didn't hit their collborative stride until Hitch's Notorius in 1946. Most of Hitch's work was with other producers and studios for which he was loaned out like any other actor or director of the time.
Nevertheless, Hitch learned valuable lessons in structuring a film for the American audience. He also managed to reach an audience that he could only have imagined before coming to America. Selznick's most valuable lesson was learning to let his directors occasionally have their way on projects.
Leff's book is a bit too scholarly in tone for the average film fan but is well written and researched. It's also quite expensive given that it's a large format paperback (this probably has to do with the small audience imagined for it and the fact that it comes from the UC Press). Many of Leff's more interesting observations have turned up as commentary on a number of Criterion DVDs (particularly the Spellbound DVD released last year).
There were many classic films produced during their time together but just as many misfires (Spellbound, despite it's many attributes is a good example of the disasterous turn their collaboration could take). Hitch hadn't hit the height of his powers as a director yet. His most powerful films (Rear Window, North by Northwest, Vertigo, The Trouble With Charlie, Strangers on a Train, Psycho and The Birds)loomed in his future. Nevertheless, his films from this time frame are, at times, revolutionary in one way or another (Saboteur, Shadow of a Doubt, Lifeboat among many others).
This book details their work together from uneasy partnership to the truce that allowed Hitch to produce one of his most magnificient films (Notorius). Although Hitch's work has come to dominate our culture more than Selznick's (with the possible exception of Gone With The Wind), neither man would have achieved his goals without the other.