Backwards compatibility?

[gamefreak180]

So I am the only person in my online group with a Copy of the 2ed book how compatible are the 1ed rules from the 2 books that were combined?

[solkan]

The 2nd edition rulebook invalidates the two almanacs (Fated and Fatemaster) but the expansion books should still work with it.  There are enough minor changes in the main rules that you'd probably get in trouble if you were tempted to look at the almanacs during the game.

A lot of Into The Steam's new rules were incorporated into the main rulebook, so there are some cases (like skill triggers, and some weapons) where you have to ignore stuff in the expansion because it's in the rulebook now.  And personally I'm not a fan of the refined magical theories.

You're better off redoing your characters than trying to use them as is in the new edition.

[Sernus]

There are quite a few differences between TtB 1E and 2E...

• There's a callout box - "Discontinued Skills" - on page 169 of the 2E Core Rules that lists all of the 1E Skills that were eliminated by being merged into the accompanying replacement Skill for Second Edition.
• Many of the 2E Pursuits in the Core Rules book are considerably changed from those of the same name in the 1E Fated Almanac. 
• The way Soulstones function in the 2E rules is very different from the way they worked in 1E, as well.

Those are just the main changes I could come up with off the top of my head... there are many, many other subtle changes, and not a few not-so-subtle ones, throughout the 2E Core Rules.  Without all manner of notes and mark-ups, I think it'll be pretty difficult to use the original Fated and Fatemaster's Almanacs as a main "go-to" rules resource.

[gamefreak180]

That is what I thought haven't looked at 1ed books yet but I had a feeling especially when reading the range immuto thread.