Vanilla 5e adheres to the kiss principle of "simple is better", which is probably part of its success, but it means there are large swaths of the game that are, well, rather sparsely fleshed out. LU's advanced 5e tries to address these gaps and oversights with interesting ideas, content and tweaks, while leaving the experience recognizably 5e to anybody who has grown comfortable with that ruleset.

If anybody in your gaming group has ever groused about 5e’s lack of a coherent crafting system, or complained about the feats being kind of boring, or they consistently ask about character backgrounds and class redesigns they found on the internet, because they’ve played all the ones in the book… but at the same time, the group isn’t interested in shifting to a new system, LU’s a5e is the answer to those problems and so much more.

Converting an ongoing 5e game to advanced 5eshould be relatively painless, and possibly really enjoyable. A lot of thought has gone into creating a more thorough character creation process, while the addition of the expertise die mechanism, which replaces and expands upon vanilla 5e’s skill expertise mechanism, subtly changes the way you play the game. Starting a new game with players that have played 5e (virtually a given with a majority of existing and new ttrpg players these days) should be a breeze compared to introducing a completely new system, which should make it easier to collect a group willing to play it together.

The only downside to the Adventurer’s Guide, specifically, is that LU’s fascinating journey mechanic is left out of it completely, instead they placed it in the companion volume, “Trials and Treasures,” which is squarely aimed at DMs (or “Narrators” as they call them). Many options during character creation specifically apply or enhance a character’s ability with the journey mechanics, but not having the mechanism explained in what is essentially a player’s handbook replacement means that many new players won’t realize why these abilities or desirable or useful, leaving it up to the Narrator to explain it to them later. Of course, the journey mechanism (I actually think of as a minigame within the system to add significance and interest to an otherwise often ignored part of an adventure, except for the repetitive “roll for a random encounter” option) is entirely optional, and it might add to the experience if tables are known only to the narrator, but it would have been good to explain the process to the players… sigh.