A sign?

I don't strictly believe this is a sign or omen, could you maybe explain more about how it got there? Like were the books open to other people? Of so, it could simply be a happy occurrence. As a feather bookmark would be pretty cool.
But, as I'm fairly certain you are strongly convinced this is indeed a sign. I'm not going to end there. As most likely you'll ignore a negative to this. (I'm only saying this because that used to be my reactions if something happened)
So, as Pers said (LokiDottir, sorry if I messed up your username, I'm not used to this one) if you want to look into this further divination is the way to go. You can do this by meditation, trance-work, runes (though runes weren't traditionally used in this fashion) or any number of techniques.
I'm also assuming, you're thinking along the lines of, if you'll try and speak to Odin, that you'll give him a prayer?
If I were you, I would give an offering. Look through this section, especially the ones done by Personified, or CleverName. Though I do not recall if either of them did a post on Odin.
Off the top of my head, mead, blood, and perhaps a task in his name would be good offerings. I still suggest research. Whenever I do deity work, I brush up on who they are, lore on them, where they are, and details on that place. And their relations. So I suggest that as well.
But I shall forewarn you, as I have a feeling you would do the task one, yes?
Odin is a bit of a.. 'No pain, no gain.' deity, with his nine days of no food or drink during his ordeal on Yggdrasil.
Best of luck

Is there any correct way to summon him? I don't have very many supplies. incense and candles are all I have, plus gems, stones,and rocks

Instead of trying to "summon" Odin (which I suggest you never try to do, because it is often seen as rude and bossy) you could make an offering to him and ask for his help.

http://www.northernpaganism.org/shrines/odin/writing/altars-and-offerings-for-odin.html

Usually, when someone would make an offering, would it acceptable to eat thhe offering? My folks would get very suspicious of they saw me bury any kiind of food...

Some practices allow you to "share", food and drink, with your deity.

It doesn't have be food/drink, as gifts of candles, incense, and objects are also accepted.

It all depends on the deity, or deities, that you wish to honor/contact.

Come on, Olivia; have some sense. Not every strange thing you come across is a "sign" from the Gods!
Your "sign" is that somebody found a bird's feather, and placed it in a book.

Every time i see this thread brought up i think of the morigan.

Thanks, Loki chains! That gives me alot of confidence~

Brysing, Everyone has a different life and a different journey to walk. I am quite sure its a sign. its the only, and first, bizarre thing that has happened to me. Plus, who would just stick a feather in a book? The feather was completely unnoticeable until I stumbled upon it. I showed my friend and fellow mentor, Asher, and he told me it was, indeed, a sign. I trust Asher very much and I am sure he would never lie to me. (He's always brutally honest.)

Very well,Olivia.I wasn't trying to insult you. As I have said many times on this site, you may believe anything you wish.
But a belief does not make it true!