The Stainless Steel Rat by Harry Harrison

In the vastness of space, the crimes just get bigger and Slippery Jim diGriz, the Stainless Steel Rat, is the biggest criminal of them all. He can con humans, aliens and any number of robots time after time. Jim is so slippery that all the inter-galactic cops can do is make him one of their own

Way of the Pilgrim by Gordon R Dickson

Shane, a gifted linguist, has spent his life learning the language of the old and powerful alien race that has conquered Earth. He has learned it so well that the interstellar masters, old hands at enslaving planets, regard him as a valuable servant.

But Shane has a secret. One day, in a rebellious moment, he invented The Pilgrim: a mysterious figure who incites rebellion and vanishes unseen, leaving a distinctive icon behind him.

Now the human underground is preparing to rebel. Shane knows how hopeless their rebellion will be. He knows, as well, that he will be unable to keep himself from taking part.

Deep in the stacks of Oxford's Bodleian Library, young scholar Diana Bishop unwittingly calls up a bewitched alchemical manuscript in the course of her research. Descended from an old and distinguished line of witches, Diana wants nothing to do with sorcery; so after a furtive glance and a few notes, she banishes the book to the stacks. But her discovery sets a fantastical underworld stirring, and a horde of daemons, witches, and vampires soon descends upon the library. Diana has stumbled upon a coveted treasure lost for centuries-and she is the only creature who can break its spell.

Book 2 - Shadow of Night

Picking up from A Discovery of Witches’ cliffhanger ending, Shadow of Night takes Diana and Matthew on a trip through time to Elizabethan London, where they are plunged into a world of spies, magic, and a coterie of Matthew’s old friends, the School of Night. As the search for Ashmole 782 deepens and Diana seeks out a witch to tutor her in magic, the net of Matthew’s past tightens around them, and they embark on a very different—and vastly more dangerous—journey.

Book 3 - The Book of Life

Diana and Matthew time-travel back from Elizabethan London to make a dramatic return to the present—facing new crises and old enemies. At Matthew’s ancestral home, Sept-Tours, they reunite with the beloved cast of characters from A Discovery of Witches—with one significant exception. But the real threat to their future has yet to be revealed, and when it is, the search for Ashmole 782 and its missing pages takes on even more urgency.

Shadow Warrior Trilogy by Chris Bunch

Ten years had passed since mankind had won the Great War. The dreaded Al'ar, loathsome aliens who killed by mere sight or touch, had been vanquished. Now they were gone, forgotten, and humanity was free to expand throughout the galaxy.
But one man remembered. Joshua Wolfe had been a hero of the Great War. He had lived with the Al'ar first as a friend and then as a prisoner. He knew their ways, knew their disciplines, knew how to kill as they killed.
And Joshua Wolfe was the only man who knew that the conflict was not over.
Before the Great War, in a time of friendship, the Al'ar had given him a name: Shadow Warrior. Now he would fulfill its lethal promise..

Misspent Youth by Peter F. Hamilton

It is forty years in the future and, following decades of research and trillions of euros spent on genetics, Europe is finally in a position to rejuvenate a human being.

The first subject chosen for treatment is Jeff Baker, the father of the datasphere (which replaced the Internet) and philanthropist extraordinaire. After 18 months in a German medical facility, the 78-year-old patient returns home looking like a healthy 20-year-old.

"Misspent Youth" follows the effect his reappearance has on his friends and family -- his young ex-model wife Sue, his teenage son Tim, and his long term pals, themselves all pensioners, who are starting to resent what Jeff has become.

Deathworld by Harry Harrison

The planet was called Pyrrus...a strange place where all the beasts, plants and natural elements were designed for one specific purpose: to destroy man.
The settlers there were supermen...twice as strong as ordinary men and with milli-second reflexes. They had to be. For their business was murder...
It was up to Jason dinAlt, interplanetary gambler, to discover why Pyrrus had become so hostile during man's brief habitation