The best quick introduction to Ortega y Gasset's philosophy in English is
The most scholarly and thoroughly researched and documented book about Ortega's philosophy is A Pragmatist Philosophy of Life in Ortega y Gasset, by John T. Graham (Columbia and London: University of Missouri Press, 1994), the first volume in a series of comprehensive studies of his thought. Here Dr. Graham, a historian specializing in the history of ideas, presents detailed evidence of the controversial thesis that Ortega's metaphysics was largely derived from the thought of William James. Two subsequent volumes deal with Ortega's theory of history and sociology.
Two more recent books presenting Ortega's central metaphysical concept of "human life as the radical reality" are: Human Existence as Radical Reality: Ortega y Gasset's Philosophy of Subjectivity, by Pedro Blas Gonzalez (St. Paul, MN: Paragon House, 2005) and Human Life as Radical Reality: An Idea Developed from the Conceptions of Dilthey, Heidegger and Ortega y Gasset, by Howard N. Tuttle (New York: Peter Lang Publications Inc., 2005).
A few years ago I set up a webpage at www.geocities.com/longknowledge/ortegaygasset.html, which was intended to be a bibliography of all works in English by and about Ortega. It does include bibliographies, books and articles, but still remains to be completed with dissertations and other materials.
I have been a student of Ortega's thought for almost 50 years. If you have any specific questions about Ortega's philosophy, I will try to answer them or at least point you in the right direction. You can contact me through the Forum or directly at [EMAIL="[email protected]"][email protected][/EMAIL].
"I am I and my circumstance, and if I don't save it I don't save myself." Ortega y Gasset, 1914