5e Book choices for making a character

[Oledirty]

I'm coming from 3.5 and I'm used to numerous prestige classes ad loads of character choices. Other than xanthars and the PHB what other choices do I have to add more flair flavor to my character. I see that multiclassing is the new norm and am alittle disappointed by this. Seems Liking making a unique character is far harder in 5e than it previously was in 3.5. Does anyone have any answers to these somewhat open ended questions lol.

[2D8HP]

I never got around to playing 3.5 (but I did buy The Complete Adventurer and the Races of the Wild "splat books") so I'm hardly an expert in making 5e more like 3.5 (1e was my game), but besides Xanthar's there's usually new backgrounds, and sometimes sub-classes in the published adventures (Out of the Abyss has the most IIRC), and while it's more of a setting book, The Sword Coast Adventurers Guide has some stuff.

You also may like some of the "Unearthed Arcana" stuff, a good list of it is:

https://www.learningdnd.com/resource/unearthed-arcana-list/

[Chugger]

A lot of us don't multi-class, or at least much - there is a big price to pay for it - some of us like being 'on time' getting new powers as we lvl up - and a lot of multiclassing does not work all that well. Or works for a bit and then fizzles out. A few, though, are quite good.

There is SCAG, EE, VOLOs for other books. In AL it's still phb +1, meaning you can only pull from one source book outside the phb.

Sword Coast Adv Guild (? - edit Guide) or scag has awesome cantrips - like booming blade and green flame blade, and a few other options.

I'm not sure what book bladesinger lives in, but it's one of them.

Iirc a lot of the EE spells are redone in xgte.

Volos is more for monster races.

[Naanomi]

Discounting new backgrounds, which are spread about various books, the ‘official’ material with character options are Player’s Handbook, Dungeon Master’s Guide, Elemental Evil Player’s Guide, Volo’s Guide to Monsters, Xanathar’s Guide to Everything, and Sword Coast Adventurer’s Guide... Tortle Package is also fairly close to official (adventure league legal anyways) as well

[Dyndrilliac]

In my humble opinion, the best bang for your buck in terms of books with crunch content (rules that are mechanically useful to your character) are the Player's Handbook, Sword Coast Adventurer's Guide, and Xanathar's Guide to Everything. If you're playing as opposed to DMing, you really don't need anything more than that unless you really want a niche option that's present in one of the other published materials.

[Falcon X]

It is exactly as minimal options as you are feeling. It is one of the greatest and worst things for a 3.5 gamer.
We respect the balance it brings to the game by restricting official content, but you sure do feel it every time you don’t look through thousands of prestige classes, skills, and feats.

This does seem to be a choice. They keep official content a minimal for balance.
However, homebrew is easier, because it is hard to break the game to an absurd amount without it being obvious.

[MxKit]

You absolutely don't have to multiclass, it's just fun for a lot of us to do! A good thing about 5e imo is that each class is solid going all the way from 1st level to 20th; in fact, a lot of multiclassing guides stress to think about what you're losing out on by taking any number of levels if a different class, and how you'll be slowing your progression in ways you really might not enjoy doing.

3.5 allows a lot of uniqueness given the tons of racial options and class options and prestige class options, and I do miss some of that. However, 5e adds a few things that balance that out, imo. Backgrounds are one thing that really help, and the way skills work is another. A lot of people like to optimize and get their main stats up to 20 ASAP, but even that's not actually necessary, and that helps too; you can invest in, say, Charisma even as a Fighter even if you don't need it at all for your class features/in battle.

Currently, just looking at the officially published in purchaseable books stuff, there are:

21 playable races, with 39 variations if you count each subclass as a unique option
12 available classes, with 80 variations when looking at subclasses
30 official backgrounds, with 35 variations (which aren't super variable but worth mentioning for flavor reasons—the difference between a sailor and a pirate or a noble and a knight, say), with the book also officially saying that your DM should allow you to make up your own unique background
Adding in things that aren't in the published books but are Adventurers League legal (so are, by all rights, official), that adds in two more races (Genasi and Tortle), one of which is divided into four subraces, so that's five more options. (Aarakocra are a kind of weird example; they're from the same thing that the Genasi are from, and solely aren't AL legal because they have a natural flying speed and AL really doesn't like that. If you count them, though, that brings the playable races+subraces up to 45 options total.) It also adds 17 more possible backgrounds.

For most of these things... You're going to want to look at the Player's Handbook, Sword Coast Adventurer's Guide, Volo's Guide to Monsters, and the Elemental Evil Player's Companion for races; there's also the Tortle package that's a standalone thing. You'll want to look mostly at the Player's Handbook and Xanathar's Guide to Everything for classes, and Sword Coast Adventurer's Guide has a few unique ones. And the Player's Handbook and Sword Coast Adventurer's Guide have most of the backgrounds, with a few unique ones in the officially published adventures, such as the Haunted One background in Curse of Strahd.

Looking into the official-as-in-by-Wizards-but-still-playtest Unearthed Arcana stuff, you get quite a few new race and subrace options, as well as both new subclasses and two entirely new classes (Artificer and Mystic) and even a single prestige class (Rune Scribe).

Compared to 3.5, these are definitely minimal choices. I especially miss all the varied player race options, myself! But it's growing, and one thing I do like about 5e is that you can have, say, three Dwarven Fighters who all feel mechanically distinct from each other—a Strength-based Mountain Dwarf Battle Master who hits hard and uses maneuvers to frighten, disarm, and knock down enemies as well as ensuring hits; a Strength-based Duergar Eldritch Knight who focuses on tanking and buffing himself with spells; and a Dexterity-based Hill Dwarf Samurai who has a Charisma score as high as his Constitution. And the Mountain Dwarf might've been your standard Soldier, or he might have been a Clan Crafter for his people; the Duergar might have been a Criminal or an Outlander; the Hill Dwarf might have been a Courtier, or he might have been an Urchin in his past and be trying to move past that. Those aren't just handwavey backstory elements, either; they give mechanical benefits so that your Crafter Battle Master is now skilled in Insight and can read people like a book, your Criminal Eldritch Knight is proficient in thieves' tools, and your Courtier Samurai textually knows who to go to for favors in the local court.

In a way, it's both harder to make 100% unique characters, and easier to make unique characters even out of the minimal and standard options and have the workings and rules of the game actually back you up on it.