This isn't a complete set of rules for 1822, but a guide from the
point of view of someone who's played 1846 to the main differences
between it and 1822. I haven't played 1822 yet - I bought it
pre-plague - so apologies for any errors.

1822 is a big game - big map, many companies, seats up to 7 players.
It's also got a lot of moving parts - special rules for particular
circumstances.

Track is "Lawsonian", not "curvilinear". What this means is that all
the exits from a tile which have track are connected.
http://www.18xx.net/tiles/e082.htm shows a tile you've seen before in
both styles of tile design; http://www.18xx.net/tiles/e024.htm shows a
tile that can't exist in a Lawsonian game.

Besides private and major companies, there are "minor companies";
these work rather like the Big 4 and Michigan Southern in 1846, with
only one token and their other abilities restricted compared to the
majors, and with an expectation that majors will buy them up.

Privates and minors don't close just because of phase changes, but
many privates close when bought up or when they exercise their special
power on behalf of a company that bought them up. However, there is a
minimum phase to buy them up - for minors that's phase 2; for privates
it may be phase 2, 3, or 5 depending on the private. Some privates can
only be bought by majors; the others can also be bought by minors
(which might then be bought by majors). Most privates lose their
revenue when bought in.

In stock rounds you bid on privates, minors, and (until phase 5) the
"concessions" that give you the right to become the Director of a
major company. You can't bid on everything both because you only get
so many "bidding tokens" and because you can't bid if everyone else
passing would cause you to go over the certificate limit.

You are much more likely to want to leave some money unspent in a
stock round, especially an early one, if you don't like the things on
offer much; also, the first player in a stock round is the one who
finished the last stock round with the most cash.

The concessions are converted into major companies in the next share
dealing round. This system means that rather than everyone starting
their own major company as often happens in 1846, some players will
have to either invest in each others' companies or start minors.

Minors no-one wants are removed. Some minors can be actively bad to
own at certain stages even bought at face value. Which ones? IDK, I
haven't played the game, but if you start a minor too low in phase 2
it can only be able to afford an L train which might immediately rust
when some joker starts phase 3.

You can't buy more than 60% of a company, but you can acquire more of
it by having it buy in minor companies you own.

The stock market is two-dimensional (this is a pretty common 18xx
mechanic); shares move right and left for payouts, and up and down if
they are sold (by anyone, not just the Director) or the company is
entirely player-owned. Very low price shares don't count against the
certificate limit. You can't "triple-jump" no matter how much you pay
out.

The way you start companies can change - the amount minor companies
start with in the treasury changes with phase as detailed in 3.3.5,
and more importantly from phase 5 onwards major companies don't start
to operate until 50% of their shares are sold (and in phase 6, the
other half of the company is automatically sold into the market
immediately).

You don't go bankrupt if you don't have money for a train; you take
out a loan. It's still really bad.

In the early game there is only one operating round between share
dealing rounds.

The rules like to talk about "exchange tokens". These just limit the
supply of extra tokens a major company can get. In 1822, there are
_24_ minors to buy in worth one token each - but a normal major can
only ever get three extra tokens by buying in minors or using private
abilities, because it only started with three "exchange tokens".

Companies start with a starting token, a token to place normally (for
L100), three exchange tokens, and a destination token. When you can
trace a route to your destination city (which is predetermined), you
must place the destination token (and you can't be tokened out of the
hex; you get a magic extra spot if need be), and if you run a train
that visits home and destination, the value of the destination city is
doubled.

In phase 2, majors lay one tile; after that they can lay two tiles
_or_ do one upgrade. Minors always get one build and can never place
brown or grey tiles. Some hexes have extra construction costs, but the
base cost of construction is nothing.

Issuing and redeeming shares is at the list price, unlike 1846 where
you issued at a price one step lower and redeemed at a price one step
higher. 

There are towns as well as cities; towns can't be tokened, and are
generally worth less than cities to run to, but still count against a
train's run. Trains just rust, they don't get the "obsolete" grace
turn. There are some funky trains - L trains score one city and
optionally one town, 2P trains never rust and can withhold or pay out
separately from the rest of your revenue, the mail contracts and
Pullman trains modify existing trains (like 1846's mail contract) and
E trains have their own special rule.

The map's got some funny locations. London has six stations, one in
each direction, for four majors and two minors - and a third minor
that picks one of those six stations to share. A major can have two
tokens in London if it buys in one of those minors, but you still
can't run a train London-London. There's a rule to stop you building
over a London station's exit and rendering the company useless.

The English Channel and France is kind of one location - it only takes
one stop from a train's run - but kind of two because if the Channel
is tokened out you can't score France.

Swansea starts with a city and a town but upgrades to a single city
(tile #57). Some cities (eg Birmingham and Manchester) have their own
special tiles, like the 'Z' cities in 1846.

There are some bits of track apparently running into the sea (eg P35
Ipswich). These just stop these hexes wanting special tiles with fewer
connnections.

Pontypool and Merthyr Tydfil are downright confusing. You can run
through one into the other but not any further (eg Cardiff - Merthyr -
Pontypool). You can only run one train across the Merthyr - Pontypool
connection, even though two lines are drawn on the board.

Routes are constructed outwards from tokens. This means that
Cardiff-Merthyr-Pontypool is a valid route for minors #19 and #21, but
not for minor #20, even though all three of them have tokens somewhere
on the route. If a major were to have a token in Cardiff, it could
acquire minor #20 (or token Pontypool) via Merthyr even though minor
#20 can't get to Cardiff.

The LNWR is also special. It's always the first major to buy, it's
divided into ten 10% shares, and it starts with two "home" tokens one
of which morphs into a double-value destination token when it connects
the two. Why? I dunno.