The Elaine Cunningham novels are my three favorite 'Realms novels, especially the Arilyn Moonblade/Danilo Thann books: Elfshadow, Elfsong, Silver Shadows. Elfshadow and Elfsong were originally part of the Harpers novel series, but after their success they were spun out into their own series, the Songs & Swords series. They are the novels that introduced the concept of the Elven Moonblades to Dungeons & Dragons, being artifact-level swords that could determine the character of whoever drew them, created through a combination of Elven High Magic and the touch of the Seldarine in old Cormanthyr, for determining which Elven House would become the royal line of Evermeet (whichever House still had the most active Moonblades among its members became the Royal House.)
Danilo is genuinely funny, and Arilyn is just cool. I remember getting one of my best friends, our main DM, to read them back in 2000, and he ended up loving them as well, and he commented that they were "very 3rd Edition." Arilyn was very evidently a single-class Fighter, without any multiclassing, and yet she was also skilled in several Thiefly things such as climbing walls and picking locks; we had just switched to 3rd Edition from exclusively playing 1st Edition (he'd been running 1E for over a decade by then) and it stood out as interesting to him that a D&D novel would have such a specifically Fighter character doing such Thievish things, so in that sense they are also "very 5th Edition."
Ed Greenwood apparently took a great liking to Arilyn Moonblade and Danilo Thann, and he included mention of their story (as of Elfshadow) and included 2E stats for them in The Code of the Harpers, which is still one of my favorite D&D sourcebooks to just sit back and read for fun, as well as learning some of the secret history of the 'Realms and the Harpers. This was back when The Harpers were still somewhat mysterious and interesting and they had the specific goals of the preservation of knowledge, preserving the balance between wild nature and civilization, and keeping most kingdoms small and preventing them from growing into large tyrannical empires, before they degraded into the ubiquitous, unbeatable, boring do-gooders lurking in every last village of Faerûn, such as they eventually became into over the course of 2nd Edition Forgotten Realms books under different writers.
Apparently the 5E 'Realms writers never realized nor understood that one of the main objectives of The Harpers was to preserve the balance between wild nature and civilization, rather than the group just "fighting Bad Guys," and that the organization counted many priests of the Seldarine, many Druids, and most of the Rangers of the North among its members in pursuit of that goal. Otherwise the writers probably should have realized that they didn't need to create a whole new organization called "The Emerald Enclave" to insert into the 'Realms just to do the exact same thing The Harpers were already doing, with even the same membership. It would have been much more fitting to make such a group along the lines of the Druid organizational structure from 1st and 2nd Edition Druid class, where there was only one Great Druid in an area and only one Grand Druid in the World, and all Druids of name level had to fight each other to attain the actual position of Druid.
Oh yeah, the book also includes the details on The Heralds, which is an organization I just love, and how they amicably broke away from Those Who Harp a few centuries ago in order to continue their mission independently and in true neutrality, without having any connections to any of the power groups of Faerûn.
