[dgatwood]

Originally Posted by Man Eating Duck

* Don't ever adjust line-height. Leave it at default. Readers will render a sensible default, many can override it if desired, but a silly value here can make it difficult to hit the correct value if you adjust the view.

This one, I disagree with. Here's why. Setting line height can make certain things possible. For example, drop caps. If you don't set the line height, it becomes highly dependent on the font, which means that changes to your font result in severe formatting breakage.

Also, for some fonts, the calculated line height ends up being less than 1.2, and if you don't force it up to 1.2 either by redesigning the font or by setting line-height, you'll end up with different layout in different readers. (Oops.)

So instead of saying "don't set it", I would say that if you are going to set the line height, never set it to less than 1.2 (many readers will ignore it if you do) or more than about 1.5.

I would also add that the typical calculated line height for 99% of fonts is approximately 1.2, so if the font you're using requires a much larger spacing to be readable, you probably chose a lousy font.

Originally Posted by Ripplinger

* Don't use huge uncompressed images within the book or for the cover. Run them through a decent graphic program to compress them, if done properly, you will not see any difference on your reading device's screen.

This one, I also tend to disagree with, for two reasons.

First, you can't include uncompressed images in a valid EPUB book. The EPUB spec only allows you to include GIF, JPEG, PNG, and SVG images. The first three are compressed bitmap formats. The fourth is a vector graphics format, and if an SVG image contains any bitmapped content (in the context of EPUB), that bitmapped content must be in one of the first three formats, AFAIK.

Second, some people read books on laptops and iPads that have retina displays. If, for example, you read a book on a 15" laptop with a retina display (2880×1800 resolution), you will see the difference if your cover image is significantly less than 1800 pixels tall.

And if your content has text (which most covers do), reducing the JPEG compression quality below a certain point will result in ringing around the sharp edges. Using PNG avoids this, but then you have no real way to increase the compression; it is what it is.

I recognize that older, slower readers might struggle with large images. If enough people are having trouble with this, you might use an image with a low-res image by default, then use media queries so that if the device has a higher resolution, that image goes away and a background-image property on the enclosing div provides a higher-resolution image, confident that any device that supports media queries also supports background-image.... That said, it is probably better to just ship with a future-proof high resolution copy and let people with ancient, slow devices either upgrade their hardware or shrink the cover image themselves.

Originally Posted by dwig

Don't ever use a JPEG or PNG that was saved from Photoshop using the "File>Save..." or "File>Save as ..." menu options, period. These are as "evil" as Word HTML files. Always use PS's "File>Save for Web and devices..." option which omits tons of PS specific extra editing info.

Like. +1

Originally Posted by Turtle91

"Convert" the image to what? If it's already a .jpg what would you convert it to?

Unless the original is a photo that is starting out as JPEG, don't do that. Always tell Photoshop or Illustrator or whatever to export a PNG or TIFF file so that you have a lossless starting point. Then convert to JPEG from there.