README: Improve the description of the project.

README.md

-# Unicode Character Data Tools
-
-- [ConScript Unicode Registry](#conscript-unicode-registry)
+# Unicode Character Database Tools
+
+- [Data Files](#data-files)
+  - [Unicode Character Database](#unicode-character-database)
+  - [ConScript Unicode Registry](#conscript-unicode-registry)
+- [C Library](#c-library)
+  - [Querying Properties](#querying-properties)
+  - [Case Conversion](#case-conversion)
+  - [wctype Compatibility](#wctype-compatibility)
 - [Build Dependencies](#build-dependencies)
   - [Debian](#debian)
 - [Building](#building)
 
 ----------
 
-The Unicode Character Data (UCD) Tools is a library for working with the
-Unicode Character Data from unicode.org.
+The Unicode Character Database (UCD) Tools is a set of Python tools and a C
+library. The Python tools are designed to support extracting and processing
+data from the text-based UCD source files, while the C library is designed
+to provide easy access to this information.
+
+## Data Files
+
+The `ucd-tools` project provides support for UCD formatted data files from
+several different sources.
 
-It provides a compact replacement for various wide-character C APIs. These can
-be used in Android applications, as the Android C library does not have full
-wide-character support.
+### Unicode Character Database
 
-In addition to this it provides APIs for:
--  querying the [Unicode General Category](http://www.unicode.org/reports/tr44/) values and groups;
--  querying the [ISO 15924](http://www.unicode.org/iso15924/iso15924-codes.html) script;
--  converting to upper, lower and title case.
+The following [Unicode Character Database](http://www.unicode.org/Public/7.0.0/ucd/)
+files from the [Unicode Consortium](http://www.unicode.org) are supported:
 
-The following data sets are used for the data tables:
--  [Unicode Character Data 7.0.0](http://www.unicode.org/Public/7.0.0/ucd/).
+*  Blocks
+*  DerivedAge
+*  PropList
+*  PropertyValueAliases
+*  Scripts
+*  UnicodeData
 
-## ConScript Unicode Registry
+### ConScript Unicode Registry
 
 If enabled, the following data from the
 [ConScript Unicode Registry](http://www.evertype.com/standards/csur/) (CSUR) is
 This data is located in the `data/csur` directory in a form compatible with the
 Unicode Character Data files.
 
+## C Library
+
+The C library provides several different facilities that make use of the UCD
+data. It provides a compact and efficient representation of the different data
+tables.
+
+Detailed documentation is provided in the `src/include/ucd/ucd.h` file in the
+Doxygen documentation format.
+
+### Querying Properties
+
+The library exposes the following properties from the UCD data files:
+
+| Property           | Description |
+|--------------------|-------------|
+| `General_Category` | A [General Category Value](http://www.unicode.org/reports/tr44/#General_Category_Values), including the higher-level grouping. |
+| `Script`           | An [ISO 15924](http://www.unicode.org/iso15924/iso15924-codes.html) script code. |
+
+### Case Conversion
+
+The following character conversion functions are provided:
+
+*  `ucd::tolower` -- convert letters to lower case
+*  `ucd::totitle` -- convert letters to title case (UCD extension)
+*  `ucd::toupper` -- convert letters to upper case
+
+__NOTE:__ These functions use the simple case mapping algorithm. That is, they
+only ever map to a single character. This is to provide a compatible signature
+to the standard C `wctype.h` APIs.
+
+### wctype Compatibility
+
+To facilitate working on platforms that don't have a useable wide-character
+ctypes library, or to provide a more consistent behaviour, the `ucd-tools`
+C library provides a set of APIs that are compatible with `wctype.h`.
+
+The following character classification functions are provided:
+
+*  `ucd::isalnum`
+*  `ucd::isalpha`
+*  `ucd::iscntrl`
+*  `ucd::isdigit`
+*  `ucd::isgraph`
+*  `ucd::islower`
+*  `ucd::isprint`
+*  `ucd::ispunct`
+*  `ucd::isspace`
+*  `ucd::isupper`
+
+__NOTE:__ Equivalents for `isblank` and `isxdigit` are not provided.
+
 ## Build Dependencies
 
 In order to build ucd-tools, you need: