Like many others who post on these well (IQ) endowed boards, I can not pick just one Author who really jumps out as my favorite. but I have a who list of top tens
Fantasy
1. Andre Norton "Witch World" and the following serries
2. Elizabeth Haydon "Rhapsody" "Prophecy" "Destiny" "Requim for the Sun"
3. Mercedes Lackey "The Bardic Voices" Publishers Ed.
4. Fritz Leiber "Swords & .... Series"
5. Ursula K. Leguin "Earthsea"
6. Patricia P. Mckilliup (sp?) "Riddlemaster of Hed"
7. David Farland "Runelords Series"
8. Peter S. Beagle "The Last Unicorn"
9. Guy Gavriel Keye "A Song for Arrabone"
10. G.R.R. Martin "A Song of Fire, and Ice"
(Honorable mentions of course being LoTR, Princess Bride, Soul Singer of Tyrnos by Ardath Mayhar, also WoT by R. Jordan), Recluse by L. E Modeste
Science Fiction (Hard)
1.Ben Bova "Mars"
2. Jack Mcdevitts (sp?) The Engines of God
3. Ben Bova "Venus"
4. Kim Stanley Robinson (Mars Series; Red, Green, Blue)
5. J. Schmidt (Ecologies of the Hub)
Science Fiction (Adventure)
1. Andre Norton "Solar Queen Series"
2. Robert Heinlein "Citizen of the Galaxy"
3. Andre Norton "The Stars are Ours, and Star Born"
4. Ursula K. Leguin "The Dispossesed"
5. Phillip K. Dick "Do Androids Dream of Electric Sheep"
6. Andre Norton "Brother to the Shadow"
Historical Fiction
1. Patrick O'brien Aubrey & Maturien Series
2. C.S. Forrester Horatio Hornblower
3. Alexander Dumas "The Count of Monte Cristo"
Classics
1. In the Sargasso Sea by Janvers