So I've spent a non trivial amount of time trying to explain bionicle to people who just want the interesting overview, so here's a prelude explaining some of What Was Bionicle's Deal, and then my recommendation of how to get into it.

Bionicle started as a mixed media franchise, where everyone working on their project in their own medium had some level of authorial power in parallel, and leadership changed hands over time, and it also was a mystery box story: Bionicle's setting is Weird, Alien, and contains several unexplained but clearly related Things, and a large part of the plot is PoV characters slowly uncovering them while in conflict against forces who are either part of Why or who also seeking out of trying to use Why for their own ends. And shockingly, the Why is mostly revealed by the end of the story.

Unfortunately, what's inside the mystery box has been rewritten or rethought somewhat as the series goes on (maybe controversial take?), so if you go deep dive the wiki which tries to synthesize everything into a coherent story and then start reading the stories your gonna face some weird whiplash of stuff simply not fitting because... it doesn't, not without some hand waving. Things as massive "is the main antagonist even meaningfully sentient, and what are they even trying to do?" got changed around like twice, even if that's kind of only obvious in hindsight.

Also, Bionicle is mostly built around plot arcs associated with a particular year, so you can say 2006 and there's the 2006 Set of Media, Characters and Ideas, which does help with progressing or looking stuff up.

Prelude out of the way, how do I get into Bionicle, in order:

1. Play Mata Nui Online Game (https://biomediaproject.com/bmp/play/web-games/mnog/)

This was The Thing that made the splash and hooked so many people, and as early media I think this is the most put together piece of media that exudes the Vibe that got people into early Bionicle. I think if there's any bionicle media you touch, it should be MNOG, it is emblematic of the era it came from and manages to do so as a mostly complete package that doesn't take too long to finish.

Recommend the 2006 version, which doesn't have saves but has pre-set parts of the story you can jump into; the game is mostly fairly kind aside from the final strategy minigame. The 2001 version is mostly a historical curiosity/completeness thing.

2. Read the books or comics.

Book List, Comic List. I also believe someone put together their attempt to create an Omnibus of all the text and comics that matter to make a coherent story in one giant PDF you can sit down and read, I forget the title but it should be easy enough to google.

I think Bionicle's strongest writing is in the 2004-2005 era books personally but that might be nostalgia talking.

The games are mostly something you can avoid aside from MNOG imo, and the movies are probably not as big a time investment if you're reading the books and contain some interesting visual design as well being one of the other sources of cooks in the kitchen (like, huge pivot in a character introduced by the movie that the main author at the time apparently wasn't aware of until he had to adapt it afaik).

3. Wiki diving for weird/interesting stuff: https://biosector01.com/

Not much else to say! BS01 is an amazing fan wiki but it does what all fan wikis do and try and synthesize what might not be coherent, but it is extremely complete and mostly exhaustive for what it's format it allows it to be

Appendices [Spell?]

A1. Maybe this should be listed earlier? but this is the most complete retelling of the Bionicle and Maori name lawsuit/story I've came across so far: https://bionicle.gay/chronicle/polyandbio. I think a lot of fans want to memory hole it was an issue, so I think it's nice to have a complete retelling here.

A2. This might be Deepest Nerd lore reding between lines, and I'm sorry for linking a Google Doc over a blog, but Original and Unused Ideas in Bionicle which is probably only interesting after you've gotten further enough into Bionicle, but it shows (and links out to more discussions) of how much Bionicle's plots and ideas changed while it was coming out and being rewritten as it came out, like how some of the initial ideas for Bionicle were metaphors for dealing with benign brain cancer, and contains a lot of interesting looks into how something like this came to be.