Dearhbird Stories by Harlan Ellison . Yes they short stores but I think he fits the bill of what your looking for . One suggestion with Ellison, always read his book Introductions , It part of the fun of reading . He is a truly great writer one the best of all time and very edgy. Other short stories to look for by him. I
have no Mouth But I must Scream, Paladan of the Lost Hour , Repenat Harlequin Said the Ticktock Man .
Bloodstone by Karl Edward Wagner This is first the book in dark fantasy series with science fiction elements . It also fits the adult requirement and It fits the strong character requirements. The main character Kane is immortal heroic villain/antihero . He is absolutely not a nice guy at all. but he's a fascinating protagonist. The book itself is well written and flat out fun to read.
The Star Rover by Jack London This is his only fantasy novel it also happens to be his least known novel and its quite anything else he ever wrote. Its the stir fo a straitjacket Deathrow inmate who while transcends mediation ( to make his existence in the jacket bearable0 discovers that he astral pjoecjt himself into his past lives at will. The book is epic in scope and scale , as journalisms access time space and history. Its a great book with interesting ,Ain character. You can find this book online via project Gutenberg.
Excavation by James Rollins An adventure in the vein of Indian jones but with lots of science fiction elements. Rollins is a a quick and fun read,.. I think you would like his novel.
Which bring another point in your quest to read books. make sure they book that you actually enjoy reading because , It difffukt to impposble to make yourself read a book that don't enjoy.
The House on the Borderland by William Hope Hodgeson This is short novel about 186 pages was originally published in 1908 and has never been out of print . Its ghost . science /fiction/ Horror novel . Its quick and excellent read . This book has been described as one the best ghost stotirsd in the English language . Its worth checking out
The Dark World by Henry Kuttner . A science fiction novel with a very usual protagonist
Black Gods Kiss. by C L Moore. comprise all of here wonderful Jirel of Joiry Stories
The Dreaming Jewels by Theodore Sturgeon . Theses Jewels can fresh reality and do many things good or evil depending upon the user.
Islandia By Austin Tappan Wright. A Utopain Novel about and that Never was but you wished existed . The book is well written with a story well told.
The City of the Singing Flame by Clark Ashton Smith one the great sci fantasy short states ever written . I think you defiantly like Smith's stories, His prose is without equal and he is a story teller with few equals. He wrote sequel to this story
Beyond the singing Flame and yes he can be very edgy There is website called The Eldritch Dark which has all of his stories on line list ed alphabetically . Other stories by him that I would recommend, Double Shadow , The Weaver in the Vault, The Death of Malygris , The Vaults of Yoh Vombus ( one the in-stations for literally inspirations the film Alien.
The High Crusade by Paul Anderson. Super advanced Aleins invade medieval England with the believe that the primitive humans will be easy to defeat. Lets hjust say, things don't work out quite the ways the Alien planned . This book is hilariously funny. !
Silverlock by John Myer Myers . A comic fantasy novels of stuck up socialite named Shandon Silverlock who get shipwrecked on Island called The Commonwealth which is populate by all the chapter of Myth and Literature . This another book that is a blast to read. Sivlerlock has one comic mishap after another trying to find his way across this Strange island. It's wonderfully funny stuff.
Conan The Hour of the Dragon by Robert E Howard one the 100 best fantasy novel ever writer , This books got everything you want.
Lest Darkness Falls by L Sprague De Camp A 20th century man named Martin Padwasy gets hit with bold of lightning and finds himself in 5th Center Rome . This was one the first alt hoister novels ever written. Its terrific book loot of humor and adventure and fun to read.
Jurgen a Comedy of Justice by James Branch Cabell . A fans satire written 1919 and banned in Boston and New York . Its story of a medieval pawnbroker Jurgen who is middle-aged and unhappily married and which he live his life over and marry the woman he really wanted . He get his wish and that when the problems really start for him. Cabell is master of Ironic Humor
His most famous quote " The optimist proclaims that we live in the best of all possible world and the pessimist fears that this is true "
The Illustrated Man by Ray Bradbury
Waystation by Clifford Simak
The Caves of Steel by Isaac Asimov
The Stainless Steel Rat by Harry Harrison
Earth Abides by George Stewart
Daybreak 2250 AD by Andre Norton
Starship Troopers by Robert Heinlein
The Humanoids by Jack Williamson
The Veils of Azlaroc by Fed Saberhagen
Bolo and Rogue Bolo by Keith Laumer
Damnation Alley by Roger Zelazny
A Canticle of Leibowitz by Walter Miller Jr
Invasion of the Body Snatchers by Jack Finney
The Stand by Stephen King
The Anubis Gates by Time Powers
Jack Faust by Michael Swanswick
Alas Babylon by Pat Frank
Dune by Frank Herbert
Tales from the Dying Earth by Jack Vance
The Uth of the New Sun series by Genre Wolfe
The Eternal Champion by Michael Moorcock
The Color of Magic by Terry Pratchett
Those listed on theater part of the list also good books and would be worth you while , Ive just run out of steam on my descriptions.