First, here are three short quotes taken from three excellent books.

Interest in Schopenhauer's philosophy is now returning after a long period of neglect. He has always been acknowledged as one of the greatest writers of German prose, but only recently has he begun to recover recognition as the only major Western philosopher to build bridges between Western and Eastern thought; as a philosopher whose impact on creative writers has never been surpassed; as possibly the greatest individual influence on Wittgenstein; and above all as a great philosopher in his own right. Many ideas which are thought of today as characteristically 'modern' received their first unequivocal expression in his pages. Not surprisingly, a new generation is feeling a need to study his work.
 
- From the dust-jacket of Bryan Magee's 'The Philosophy of Schopenhauer' (Clarendon Press, 1983)
.
[Schopenhauer] shared with the romantics the rejection of science, and the celebration of the aesthetic and the creative. His metaphysical position was that the world is a transcendental illusion; reality is first to be found within ourselves, and then not as reason but as irrational, impersonal Will. It is the Will that throws us this way and that through desire and emotion, but it is never under our personal control. The Will is in no sense a personal Will (any more than Hegel's Spirit is personal); it is ultimately the reality of all things, most obviously in the case of other living creatures whose lives are no more - and no less - meaningful than our own. On the rational foundation built by Kant, Schopenhauer demonstrates that life is intrinsically absurd. At best we might see our way through the absurdity, and achieve some sort of quasi-Nirvanic peace by denying the Will and the futile desires that are its most immediate manifestations.
 
- Robert C. Solomon, 'Continental Philosophy Since 1750' (Oxford University Press, 1988), pp. 75-76
.
The idea which allowed his monumental book ['The World as Will and Representation'] to take shape was his conception of the will. In the finished work, as its title indicates, Schopenhauer presents the world as having two sides, that of Vorstellung (representation), or the way things present themselves to us in experience, and that of Wille (will), which is, he argues, what the world is in itself, beyond the mere appearances to which human knowledge is limited. ... His notion of will is probably best captured by the notion of striving towards something, provided one remembers that the will is fundamentally 'blind', and found in forces of nature which are without consciousness at all. ... Schopenhauer thinks ordinary existence must involve the dual miseries of pain and boredom, insisting that it is the very essence of humanity, indeed of the world as a whole, that it should be so.
 
- Christopher Janaway, 'Schopenhauer' (Oxford University Press, 1994),
p. 6.

•  Note. There are also some Schopenhauer links on our Links Page.