Customization

Reading is personal — the whole point of a good ebook reader is that you decide how a book looks. Readest lets you tune pretty much everything about the reader surface, from themes down to individual line-height values. Changes apply live, so you can tweak while you read.

Find settings under Font & Layout in the reader, or the global Settings (Cmd+, / Ctrl+,) for defaults that apply to new books.

Per-book vs global settings

By default, anything you change in Font & Layout becomes a global default — it applies to the book you're reading and to every other book, current and future. That's what you want most of the time: set your line height once and every book inherits it.

But sometimes one book needs special treatment — a cramped textbook that wants a larger font size, or a fixed-layout title that needs different margins — without disturbing everything else. For that, turn off Global Settings:

Open Font & Layout while reading the book.
Open the ⋮ menu at the top of the settings panel.
Click Global Settings to toggle it off (the checkmark disappears).

From then on, every change you make is stored with that book only and is reloaded automatically each time you reopen it. Your global defaults stay untouched, and other books keep following them.

Themes & color mode

Built-in color modes:

Light — standard white background
Dark — dark background for night reading
Auto — follows system preference

Beyond the built-ins, you can edit background, text, and accent colors directly to build your own theme. Add a textured background image with opacity/size controls for a more paper-like feel — the library and the reader each get their own texture, so open the picker from the bookshelf to style your library or from the reader to style the page.

Fonts

Readest separates serif, sans-serif, and monospace selections — the reader uses the right one depending on the book's markup.

Bundled fonts — several carefully chosen typefaces are included (varies by platform).
System fonts — pick any font installed on your device.
Custom fonts — upload your own .ttf, .otf, .ttc, or .woff2. Uploaded fonts appear in the font picker.
CJK font override — a separate slot for Chinese / Japanese / Korean text, independent of the main Latin font.

Font weight and size are both adjustable. The size slider is fine-grained, so you can land on exactly the size that works for your screen and eyes. Want one book larger than the rest? Give it its own font size with per-book settings.

Typography

Fine typography controls:

Line height — 1.2× to 2.5×. Defaults around 1.6×.
Paragraph margin — space between paragraphs.
Word spacing — fine-grained, positive or negative.
Letter spacing — typographic refinement for certain fonts.
Text indent — first-line indent on each paragraph.
Full-width justification — on or off.
Hyphenation — language-aware line-break hyphens.

By default, Readest respects the book's own stylesheet. Toggle Override book fonts / layout / colors independently to let your own settings take precedence. This is especially useful for EPUBs that ship opinionated but poorly-tuned CSS.

Layout & writing mode

Columns — 1 or 2 columns in paginated mode, with configurable gap.
Margins — top, bottom, left, right. Separate compact margins for the header/footer chrome.
Writing mode — horizontal (LTR or RTL) or vertical — supports Chinese, Japanese, and classical Mongolian text flow.
Max width / height — caps for very wide screens so lines stay readable.

See Reading › Page layout for the paginated-vs-scrolled choice.

CJK typography

For Chinese, Japanese, and Korean text, Readest adds a few CJK-specific knobs:

CJK font — a separate font slot independent from the Latin font.
Chinese variant conversion — convert between Simplified and Traditional on the fly. Supported variants: s2t (Simplified → Traditional), t2s, t2tw (Traditional → Taiwan), t2hk (Traditional → Hong Kong), s2twp (Simplified → Taiwan, including phrase conversion), tw2s, hk2s, tw2sp.
Vertical writing — full-book vertical layout for classical Chinese and Japanese texts.
Japanese furigana — selecting Japanese text skips the furigana (ruby) readings, so copy, translation, and highlights capture just the base text. The furigana still reads aloud and turns up in search.
Speed Reading (RSVP) — Speed Reading Mode, in the reader's View Options menu, flashes one word at a time. Tune the pace with a Start Delay countdown and a Punctuation Delay, step through word by word (, and ., or skip 15 at a time with Shift+← / Shift+→), and look a word up in the dictionary without leaving the overlay. For CJK passages it adds Character Mode (advance one character at a time) and Highlight Word, so segmentation and focus land correctly on Chinese, Japanese, and Korean.

Custom CSS

For anything the settings UI doesn't cover, Readest has a Custom CSS editor — two slots, one for book content and one for the reader UI chrome. Paste any CSS, save, and it applies immediately.

Find it under Reader → Font & Layout → Custom → Custom CSS.

The book-content editor targets the rendered book HTML: body, p, blockquote, img, a:any-link, and everything else inside an EPUB. The UI-chrome editor targets the toolbars and progress indicators: .pages-left-number, .pages-left-label, and similar helper classes.

For ideas, worked examples, and the full selector list, see the Custom CSS wiki page.

E-ink mode

Readest detects many e-ink devices (Onyx Boox, Kindle, Kobo, and similar) and automatically enables e-ink optimizations:

Reduced or zero animations (no fade, no flashing)
High-contrast colors
Simpler layout transitions

Three modes are available under Settings → Behavior → Device → E-Ink Mode:

On — force e-ink mode on. Useful if auto-detect missed your device.
Off — disable even on detected hardware. Useful if you're mirroring an e-ink Android tablet to a color display.

For color e-ink devices (like the Boox Go Color), enable the color e-ink option to allow a limited color palette.