One of the great poets of the 19th c., a friend of Lord Byron and Keats, married to Mary Wollstonecraft (Frankenstein's author), Percy Bysshe Shelley (1792-1822) was a genius. He had a tragic death by drowning, when he was 30 years old, but he left a wealth of poems, essays and plays.
Because of his unconventional life and opinions and his hard criticisms, only after his death were his works truly valued for their worth. Most of them weren’t published during his lifetime.
But his influence reached some of the brightest minds of the next generations, including those of George Bernard Shaw, Isadora Duncan, Henry David Thoreau and Gandhi.
Percy Shelley was son of a Knight and member of the Whig party, he had an idyllic life at home and a hellish one at school, mainly in the aristocratic Eton College, which he joined at age 12. One of the most characteristic events of his life was his expulsion from Oxford University in 1811.
Shelley was already writing stories and had very progressive political views, which most of his contemporaries frowned upon. That year, he published the novel St. Irvyne, or, The Rosicrucian and the pamphlet The Necessity of Atheism, and was expelled after confirming his authorship. His father then intervened to get him back into college, on the condition that he would recant the writing, but when Percy Shelley refused to do so, he not only left the chance of getting back to Oxford for good, but also fell out with his father.
Other examples of his uncompromising and unusual opinions are the following quotes:
“Death is the veil which those who live call life. They sleep, and it is lifted.”
“Fear not for the future, weep not for the past.”
“Government is an evil; it is only the thoughtlessness and vices of men that make it a necessary evil. When all men are good and wise, government will of itself decay.”
“Man has no right to kill his brother. It is no excuse that he does so in uniform: he only adds the infamy of servitude to the crime of murder.”
“Obscenity, which is ever blasphemy against the divine beauty in life, is a monster for which the corruption of society forever brings forth new food, which it devours in secret.” 
Below is an excerpt of the poem Alastor, or the Spirit of Solitude (which is almost autobiographical) followed by Queen Mab. Enjoy and dream a little....
There was a Poet whose untimely tomb No human hands with pious reverence reared, But the charmed eddies of autumnal winds Built o'er his mouldering bones a pyramid Of mouldering leaves in the waste wilderness: A lovely youth,--no mourning maiden decked With weeping flowers, or votive cypress wreath, The lone couch of his everlasting sleep: Gentle, and brave, and generous,--no lorn bard Breathed o'er his dark fate one melodious sigh: He lived, he died, he sung in solitude. Strangers have wept to hear his passionate notes, And virgins, as unknown he passed, have pined And wasted for fond love of his wild eyes. The fire of those soft orbs has ceased to burn. And Silence, too enamoured of that voice, Locks its mute music in her rugged cell.
Hath then the gloomy Power Whose reign is in the tainted sepulchres Seized on her sinless soul? Must then that peerless form Which love and admiration cannot view Without a beating heart, those azure veins Which steal like streams along a field of snow, That lovely outline which is fair As breathing marble, perish? Must putrefaction's breath Leave nothing of this heavenly sight But loathsomeness and ruin? Spare nothing but a gloomy theme, On which the lightest heart might moralize? Or is it only a sweet slumber Stealing o'er sensation, Which the breath of roseate morning Chaseth into darkness? Will Ianthe wake again, And give that faithful bosom joy Whose sleepless spirit waits to catch Light, life and rapture, from her smile?
More info: Percy Bysshe Shelley