Books?

I recently created a level 1 Wizard on D&DB, and his equipment pack came with a book. 

I clicked on it and it said, "A Book contains fiction or nonfiction. If you consult an accurate nonfiction Book about its topic, you gain a +5 bonus to Intelligence (Arcana, History, Nature, or Religion) checks you make about that topic." 

So can I declare my book is a nonfiction book of Arcana, and now I have a +5 bonus on Arcana checks? That's a pretty good bump at first level. 

Anyone use this mechanic for books at their table? 

That is not exactly correct. "Arcana" is not a topic. "Spells creating illusory effects in the real world" is a topic. And INT checks about that topic tend to only give you more information about that topic.

Is there a source for that interpretation, or is that how your DM uses the rule? 

Quote from dguyellison >>

Is there a source for that interpretation, or is that how your DM uses the rule? 

There's no specific definition of "topic" within the rules, though if the intent were for you to pick an entire skill for it, surely it would've said "a skill" instead of "a topic".

Quote from dguyellison >>

Is there a source for that interpretation, or is that how your DM uses the rule? 

It is definitely up to the DM as to how general your topic can be, but wagnarokkr has a good point that Arcana, History, etc. are skills, not topics, per se. It's also important enough for me to repeat: the INT checks using these skills are almost always used to simply discover information. A +5 to learn a little bit more about something (even if it does end up being very general) isn't all that powerful.

This is the kind of thing that will be clearer when playing. A lot of adventures contain books in their loots on specific topics you can take inspiration from. 
Like "a book on the biology of red dragons" for example. Or "a book about the history of Neverwinter"... things like that.