That is definitely a typo!
It should say "When you prepare a spell..."
I am giving the book away for free! It's also CC-BY-SA and all the art is public domain. Folks can do with it what they will.
As for more content.... It's coming. An adventure and bestiary. In the works!
Print version should go up this week!
There are actually four body slots if you include hands. You could have Chainmail (2 armor/bulky) and and a helmet (1 armor/slot), using three total slots, and a fourth for whatever weapon. Of course, if a player wanted to use two slots (e.g. for a bulky weapon) I'd let them; fictionally I'd say they would just carry less in their backpack because of the cumbersome nature of all that armor + weapons.
I guess the Cardinal Rule is: fiction first. If the PC was mutated (and sprouted an extra arm) I probably wouldn't give them extra slots, but I would let them wield three knives.
PS I kinda assume stuff like Plate Mail has a helmet attached (since it gives 3 armor). I'd even be OK with saying that Chainmail (2 armo/bulkyr) + helmet (1 armor/slot) sorta combine together, and use one backpack slot. Of course, different Wardens will rule as they see fit.
Is the art CC-BY-SA as well as the text? I'm wondering, as some of the weapons are really great and would work really well as tokens for online play. I'm always looking for some (like that sweet sling in Shadowlords) to distribute in my own free game, Cairn.
Oh that's a great idea. And yes I've found that as long as you give a simple 1 HP per HD it seems to work out well (and all credit goes to Into The Odd being so brilliant). I like to add +2 HP to larger foes, as well.
If the game is a hack, go wild. Mix and match. As long as it has bits of Into the Odd in it, I'd say it's fine.
For content, try to keep within the basic rules (which are pretty lean already). That means auto-hit damage, three stats, failed careers, etc. That said... Who cares? Do what you like. Chris wrote a blogpost about what are essentially classes the other day, and the game was still the same otherwise.
Basically just absorb the rules and twist however you like. Maze Rats was based on Into The Odd, but became something completely different in the end. I'm pretty sure Ben Milton still considers it a hack, though.