Oh dear, you've gotten me started on Dorothy Dunnett ... beware what you ask for!
Here goes ...
First, she didn't write sci-fi or fantasy, so since this is off topic for this discussion, I'll keep it brief, or move further info to the Library discussion if you guys want more.
Ok, in brief, Dorothy Dunnett was (she died in 2001) a Scottish writer of historical fiction, who has a very enthusiastic and devoted fan base. She is most famous for her 6-book series of novels, "The Lymond Chronicles," which together span roughly the period of time from Henry VIII's death to the ascension of Elizabeth to the throne. The settings range from Scotland, England, France, Russia, Turkey and spots in between. The hero, Francis Crawford (Lymond), is fascinating: he's beautiful, brilliant, suicidal (literally), tormented, cruel, loving, misunderstood, a master swordsman and soldier, a great leader, a talented musician. Once you've met him, you'll never forget him.
The first book in the series is "Game of Kings." As it's the first book that Dunnett ever wrote it has some stylistic quirks (like little tags in foreign languages) that are dropped in the later volumes, but ignore those and persist. Some of us are hooked from the first words, others have reported that it took them until about 50 pages in to become fully engaged.
Whichever is the case for you, if you like vivid, well-researched, adventurous historical fiction, you should read it. Hint: it has the best sword fight scene I have ever read (Dunnett is a master of the action set-piece).
Also, be warned: the first book can be read on its own as can the second, but the third, fourth and fifth books all end on cliffhangers and if you get that far, you'll be reading them end on end far into the night.
For more, check out the reviews for "Game of Kings" on Amazon.