[pssquirrel]

I'm sure jackie_w will provide a more complete explanation, but some quick examples in the meantime:

Sample code for using fonts already installed on your T1 (you'll find a list of the built-in fonts in the Wiki):

Spoiler:

@font-face {
font-family: serif;
font-weight: normal;
font-style: normal;
src: url(res:///ebook/fonts/AmasisMTW1G.otf);
}

@font-face {
font-family: serif;
font-weight: normal;
font-style: italic;
src: url(res:///ebook/fonts/AmasisMTW1G-Italic.otf);
}

@font-face {
font-family: serif;
font-weight: bold;
font-style: normal;
src: url(res:///ebook/fonts/AmasisMTW1G-Bold.otf);
}

@font-face {
font-family: serif;
font-weight: bold;
font-style: italic;
src: url(res:///ebook/fonts/AmasisMTW1G-BoldItalic.otf);
}

body {
font-family: serif;
line-height: 100%;
}

NOTE: You can change the line-height to whatever you like -- 100%, 120%, 150%, etc.

Sample code for using your own fonts (create a "fonts" folder in your "reader" folder, then copy your fonts into the "fonts" folder):

Spoiler:

@font-face {
font-family: serif;
font-weight: normal;
font-style: normal;
src: url(res:///ebook/fonts/../../mnt/sdcard/reader/fonts/MYFONT.ttf);
}

@font-face {
font-family: serif;
font-weight: normal;
font-style: italic;
src: url(res:///ebook/fonts/../../mnt/sdcard/reader/fonts/MYFONT-ITALIC.ttf);
}

@font-face {
font-family: serif;
font-weight: bold;
font-style: normal;
src: url(res:///ebook/fonts/../../mnt/sdcard/reader/fonts/MYFONT-BOLD.ttf);
}

@font-face {
font-family: serif;
font-weight: bold;
font-style: italic;
src: url(res:///ebook/fonts/../../mnt/sdcard/reader/fonts/MYFONT-BOLDITALIC.ttf);
}

body {
font-family: serif;
line-height: 100%;
}

NOTE: You can change the line-height to whatever you like -- 100%, 120%, 150%, etc.

Don't forget to update your reader.xml file with the proper font names and filenames:

Spoiler:

<styles default="/mnt/sdcard/reader/css/default.css">
<style name="FontNameA" file="/mnt/sdcard/reader/css/FontNameA.css" />
<style name="FontNameB" file="/mnt/sdcard/reader/css/FontNameB.css" />
<style name="FontNameC" file="/mnt/sdcard/reader/css/FontNameC.css" />
<style name="FontNameD" file="/mnt/sdcard/reader/css/FontNameD.css" />
<style name="FontNameE" file="/mnt/sdcard/reader/css/FontNameE.css" />
<style name="FontNameF" file="/mnt/sdcard/reader/css/FontNameF.css" />
</styles>

Note: CSS rules can be tricky. The above is bare-bones and just enough to get people started. It will work for many but not all epubs, depending on how they're formatted.