This is an early Deleuze book, back from his days of grounded & thorough research on obscure but respectable philosophers, yet this supposed 'study' of Bergson is already quite independently Deleuzean philosophy in its own right. His main project is to try and make sense of the relationship between Bergson's famous concepts . . . . he begins by stridently declaring that Bergson's philosophic method (usually understood as a logical series of arguments against the Neo-Kantian perspective) is in fact a primarily linguistic and eisegetic response to basic philosophical dilemmas such as the mind-body problem. Bergson's solutions, he claims, always follow a confounding path that perpetually leads to a deflation of space and a centrality of duration, a method that produces a time-centric philosophy that dispenses the centrality of scientific and mathematical partitionings. By this method, then, Bergson arrived at the mystic nature of time, the ontological split between memory and present experience, and his organic/morphological revision of Darwin's theory of evolution.
However, when Bergson's distinctions are taken not as corrections of standard philosophic frameworks (as Bergson sought to do in rejecting, eg, the materialist-idealist divide) but rather as synthetic creations within the basic Hegelian mode of the 19th century, Deleuze feels that Bergsonism produces bizarre paradoxes. Matter and Memory, for example, simultaneously argues for a pure monism of spirit (in that the psychological distinctions of the mind are partitions of a united manifold) and for a fundamental gap between past and present (in that the mind necessarily functions on the duplicities within that manifold); likewise, Bergson writes variously on time that its passage is relativist and variable based on experience, but also that its special nature must derive from an external and independent unity of substance. Deleuze, then, attempts to make sense of Bergson's own solution to these paradoxes between monism and multiplicity, namely, Bergson's sense of a unity of spirit that is partitioned variously by the Soul, a perennially relevant process that is as true of an individual's experience of the world and mind as of the organic evolution of life as a whole. This is essentially a variation upon the Platonic theory of the Good, but where Bergson differs (or at least may seem to) is in totally subjectivist and 'living' nature of ontological and philosophical distinctions ... as opposed to classical idealist philosophy, where distinctions are drawn 'negatively' to ascertain noumena, Bergsonism then (allegedly) draws its distinctions in a positive way: just as the mind separates one object from another to create positive concepts, so too does Bergson's philosophy creatively and actively partition logical arguments for the sake of creative, organic solutions.
This, of course, is perhaps true or untrue of Bergson's philosophy proper; it is absolutely true, however, of Deleuze, who managed to attribute a nigh identical attitude to Spinoza on the higher-order levels. Indeed, just like with everything and everyone Deleuze wrote about, it turns out that Bergson was simultaneously a machine and an indeterminably living being who theorized schizophrenically about DIFFERENCE and REPETITION. What's interesting about this method of 'philosophical criticism', as it were, is that it is simultaneously so radically transformative and yet never quite logically objectionable, at least not on any petty levels. Bergson here is made practically to transform into a late Heideggerian lingusitic-processor, and then into a Deleuzean machine ... depending on yr creed you may find this a genuine study or else a sophistical challenge to be overcome (or both!), but definitely a worthy study for anyone interested in Bergson or Deleuze; do not be fooled by its shortness of length, for its density and scope of argumentation seem to me to be equal to any of the great tomes of the philosophers.