There are many aspects to learning the creation of interactive fiction. Here we mostly undertake to explain approaches to using Inform, and leave the larger questions of craft and design for elsewhere.
The two manuals
There are two interlinked manuals built into every copy of the Inform application: if you've downloaded Inform, you already have them. But they are also available to read or download separately from this website.
Writing with Inform is an overview of the language, beginning with the simplest kinds of construction (such as building a map of rooms, objects, and doors) and working its way up to more advanced tasks. It is meant to be read more or less sequentially, since later chapters build on the ideas in earlier ones; though some of the late chapters (such as those covering numbers, activities, or advanced text) might reasonably be read out of order.
The Recipe Book approaches the problem of authorship from a different perspective. Instead of trying to teach the language from start to finish, it is organized for the author who wants to accomplish something specific, such as asking the player's name at the start of play or implementing a system of measured liquids. It shares the same set of examples that are keyed to Writing with Inform, but organizes them into a new order and accompanies them with text about design problems in creating interactive fiction, rather than explanation of language features.
Following requests from partially sighted Inform users, we've also made two plain vanilla versions of the manual available - they have as little decoration or web design as possible, which means less clutter for screen-reading software to cope with. We offer a choice of:
Minimally tagged HTML provides an archive containing the pages of the manuals and examples as vanilla-flavoured HTML files.
Writing with Inform in plain text format is just what it claims to be - one single file containing only text, with no marking-up of any kind. This contains all of the examples, following the text in numerical order, but not the Recipe Book. (The whole idea of two interleaved manuals can't really be achieved in one flat text file.)
We receive occasional questions about publishing a printed form of the manuals. The answer is that we intend to do exactly that, in due course, but that we expect the current text will be revised wholesale once the system is more mature. (The same thing happened with Inform 6, with the appearance of the printed Designer's Manual in 2001 essentially marking the end of its design cycle.)