Can you get the journal Entries by killing monsters or only by reading?

From what I remember, both, but you can harvest more monster parts, if you read, so more money you can do...also it was in Inteligence tree something about harvest from monsters not read it yet(or plants)...

There are a few entries that can be gained by spending a Talent (they can also be got in other ways, taking longer but letting you spend your Talent on something else). Most are gained through talking to people (in some cases it's necessary to give them things) or reading books.

[url=http://witcher.wikia.com/wiki/Category:The_Witcher_bestiary]http://witcher.wikia.com/wiki/Category:The_Witcher_bestiary[/url] entries are often useful at listing sources, but obviously they comtain spoilers.