Is there any halfway-short-ish history/timeline or a starting point in a wiki of the 40k (and apparently 30k as well?) universe that I could read?
"Short" and "40k background" tend not to go hand-in-hand. Lexicanum is a pretty good source if you like getting lost in wiki articles. A lot of previous editions of the 40k rules and most Codexes (Codices?) have a timeline outlining important events, but some more recent additions like the War of the Beast aren't present in a lot of them. It also kind of depends on the perspective of the faction. If you want me to put together some kind of summary I'd be happy to, just send me a DM.
Well moving on to news - again I've been lazy and suddenly get overwhelmed by stuff! I'll try to keep it short but you all know by now I have a tendancy to ramble when I'm excited.
Tactical Reserves: Traditional reserves stuff like Deep Strike and Outflank are gone and any model with a similar ability will have a bespoke rule for it. I like this, it means they can be flexible without adding exceptions like "Can deepstrike but only roll 1D6 scatter" or "Can assault after deepstrike" and whatnot. Now they can just say "Set up X inches away from enemies then you can/can't/maybe act normally". We get the Trygon as an example, who can burrow up 9" away from enemies, bring a unit of troops with him, then assault. Nice. It also mentions that only 50% of the army may be held in reserves, so no more null deploy alpha strike BS. In matched play at the end of the 3rd battle round anything left in Reserves is destroyed automatically. Interesting that they say "Battle Round" instead of "Game Turn". Could this be an early hint that AoS style roll-for-turn could be implemented?
Faction Focus Drukhari: Dark Eldar get an article and a fancy new name! Not unexpected. Nothing too telling in this one, just the usual prep-talk about how cool the army is. It does show a rule for Wyches that has a chance to prevent fleeing from combat, which is something I expect to see on other units as well, albeit fairly uncommon.
Vehicles: Vehicles no longer have their own unique stats, they get the same profile as everything else now! It seems that they're trending to be middle-high to high toughness and middling armour saves (3+ or 4+), banking on a large number of wounds for protection. They also have WS. S and A characteristics. An interesting move, but kinda makes sense. I'm so used to being able to charge a tank with no fear of repercussions so it will take getting used to, but realistically a tank isn't going to sit still and do nothing while a bunch of chainsaw wielding psychos wail on it! Vehicles also suffer from shooting penalties for movement, but I imagine tanks like Leman Russ or Landraiders to have some way to ignore this.
Close Combat Weapons: Pretty much what I expected, the profile format is largely unchanged but the details themselves are different. USRs like Shred, Unwieldy and Fleshbane are gone, but each weapon has a "Special Rules" column for any bonuses beyond the profile. A fair few profiles were revealed too, which I won't post here for the sake of saving space. Two big ones (for me anyway!) are: with Initiative gone Power Fists have a penalty to-hit rather than striking last, and Chainswords get to attack one extra time whenever the wielder fights. Time to dust off my Berzerkers.
Faction Focus Imperial Knights: Again another fluffy "this army is great" article. This time we get our first PROPER look at degenerating stat lines, and it's pretty much exactly the same as AoS. Knights have a crazy amount of wounds (24) and you have to strip off half of them before they start feeling the pain, but we'll probably see the same kind of thing applied on a smaller scale to regular vehicles too. Stomp attacks are also gone, replaced with the "Titanic Feet" rule for the Knights. A bunch of their weapons stats are littered throughout the article which I won't go into, but suffice to say they look good. There's also the Superheavy Detachment, which consists of 3-5 Lords of War. Sorry guys, the Superheavy spam isn't over!
Stronghold Assault: So Stronghold Assault seems to be rolled in to the Narrative way to play. It's what you'd expect, attacker and defender. Each side has different Stratagems depending on which role they take, and there's some extra rules for demolition and capturing buildings. I've always liked these kinds of games but by being an "extra layer" of rules on top of 7th we just never really used them. Lets hope that I get to lay siege to some Imperial Scum in 8th!
Transports: This is one everyone was on the edge of their seats waiting for. They don't go in to the mechanics much, but we now know a few key things. You must disembark BEFORE the transport moves. Big change. Units can behave normally after disembarking, and that includes being able to charge. Another big change. If a transport explodes, roll a dice for each model and on a 1 they're dead. Hugely beneficial to anyone who isn't a Space Marine, where exploding transports were a deathtrap that would see your unit ruined. One thing that was mentioned was that a potential tactic could be disembarking your combat units, then having both the transport AND the unit charge the enemy. Chaos have had cool ways to make tanks killy up close in the past, so I'm hoping we see more of that in 8th.
Faction Focus Tyranids: More of the same. They seem a bit like Seraphon, in that they benefit a lot from synergy and leaders passing out buffs and units improving the more models they take. Looks like PROPER Tyranid armies could make a comeback. They were my first army ever, so it would give me a warm fuzzy feeling to see swarms of Gaunts racked up with some big gribblies behind them for support.