in Production
Cream paper or white
The colour of a book's paper affects how it reads, how its images print and even how thick it is. It is worth choosing on purpose.
Most book papers come in two broad shades: a warm off-white usually called cream, and a brighter white. The choice looks minor. It affects how the text reads, how images reproduce, how the book feels and, depending on the stock, how thick the finished book is.
Cream paper is widely used for fiction, memoir and other books meant for sustained reading. White is more common for non-fiction with charts or photographs, textbooks, workbooks and books where images matter.
These are tendencies, not rules. Plenty of novels are printed on white, and plenty of non-fiction on cream. But the association is common enough that many readers take cream as bookish and bright white as practical.
Reading comfort
Cream paper reduces the contrast between black text and the page. Many readers find that gentler over long stretches of reading, particularly under bright light. White paper gives crisper contrast, which suits reference use, small type and shorter reading sessions.
Neither is objectively better. The choice is about the kind of reading the book invites. A long novel is read continuously for hours; a manual is consulted in short bursts.
Images and colour
Paper colour affects everything printed on it. Printing inks are partly transparent, so the paper shows through them. On cream paper, colours shift warmer, the whites in a photograph become the colour of the paper, and cool blues and greys can look muddy.
For a text-only book, this hardly matters. For a book with black-and-white photographs, cream can give a pleasant warm tone or a flat, dull one, depending on the images. For colour photography, white paper is almost always the better choice, and print-on-demand services often offer colour interiors only on white.
Line drawings, diagrams and maps usually print well on either, though fine detail in pale tones looks weaker on cream.
Thickness and spine width
Paper stocks differ in thickness, and a cream stock and a white stock from the same printer are not necessarily the same. Paper thickness, together with page count, determines spine width, so switching from one to the other can change the spine, sometimes enough that the cover has to be adjusted.
This is why the paper should be chosen before the cover is finalised. The printer's specification or cover template will give the spine width for the specific stock and page count.
Opacity matters as well. A thin, low-opacity paper lets text show through from the other side of the page, which is distracting whatever the colour. A printed proof is the best way to judge it.
Choosing
Start with the content. Continuous text and a reader settling in for hours point towards cream. Images, colour or a practical purpose point towards white. Then look at comparable books in the category, and at the options the printer offers for the chosen trim size and binding.
If in doubt, order a proof on each stock. Paper is best judged in the hand, in daylight, with the actual text printed on it.