The lines of type in this blog are like most blogs and websites and a growing number of magazines and books. The type is "flush left/ragged right.” Ragged right ("rag-right") is much easier to produce, and people accept it.
Justified type has a more formal, polished look. Ragged is obviously less formal, but people can rightfully claim that justified type is abnormal and artificial, and ragged right is normal and natural.
Justified type is still the dominant format for book printing. It can look beautiful, but takes more time and money to do right. The block of text shown below is from one of my books. I won't assert that it's beautiful, but it's better than a lot of text from self-publishers -- and it's easy to produce with Microsoft Word. If I can do this, so can almost anyone.
A lot of very ugly justified type gets printed, particularly in newspapers with narrow columns (below).
The problem exists in narrow book columns, too (below). Sometimes the only way to improve the word spacing is to switch to rag-right, or make the column wider. You can also experiment with changing some words, which can take a long time, may be futile, and may not be an option.
There is an unfortunate trend with self-published books to use justified type, but no hyphens, which leads to really UGH-LEE word spacing.
I recently purchased U-Publish.com 5.0, co-authored by Dan Poynter. This book has no hyphens, and the word spacing (below) is atrocious.
Just as poor voice quality with cellphones and VoIP service has led to the acceptance of "low fidelity" phone conversations, I fear that ugly eBooks will increase the quantity and acceptance of ugly pBooks. It is sad, avoidable, and unforgiveable. EBooks designed for reflowable text and user-selectable type size (not PDF eBooks) can produce some terrible-looking pages (below). Kindle’s display flexibility can produce very ugly results. This is part of Treasure Island by Robert Louis Stevenson.
My first (2008) self-published Print On Demand book, I Only Flunk My Brightest Students -- stories from school and real life, is very informal. Ragged right seemed to be appropriate for the mood of the book, and it saved time.
My second POD book, Phone Systems & Phones for Small Business & Home, is more formal, more expensive and is intended to be a reference book for business people. Justified type seemed appropriate, and I was willing to invest the extra time to make it look traditional.
When I finished my tedious labor, I was so pleased with the results, that I decided to re-do the "flunk book" with justified type, while I was making other modifications and corrections.
TIP: Be careful if you are justifying a book that was already completed with ragged right type. Most lines will expand to the right margin, and sometimes words that used to fit on one page will "creep" onto another page. You may have to change the page numbering for chapter beginnings, or cut words or make illustrations smaller to get what you want.
TIP: Sometimes the spaces between words will look lousy, and you'll have to experiment with hyphenation, and sometimes switch to shorter or longer words, or add or subtract words, to make things look right.
TIP: Be very careful to check the last line in a paragraph. Sometimes even three words are spead out full-width, and they'll look very stupid. You can just select the line and re-do it as flush-left, or (in MS Word) tap the Enter key after the last word in the line.