riddle - What's Happening on my Vacation?

I'm on vacation right now! I left on the 13th in celebration of my birthday! It was a long flight so I brought along some reading material:

Faulkner, William. The Sound and the Fury. Published by Voyager Company in 1992.
D8.46 -A4.1C


Hemingway, Ernest. The Old Man and the Sea. Published by Scribner in 1995.
D5.22 D.CB

Lee, Harper. To Kill a Mockingbird. Published by Grand Central Publishing in 1988.
59.24 56.C4

****Not part of the puzzle: Let me know if you can't find any of these books. ****

I can't recall what those strange codes I wrote down were. Probably to help me remember where I am! I'm so absentminded...

Anyways, I love it here. I thought I would be out in the middle of nowhere, but it seems I'm always in the centre of the hustle and bustle.

For some reason, I'm worried about where I currently am. Can you figure out where I am, and tell me why I shouldn't be so worried?

$$\_\_,\_\_,\_\_,\_\_,\_\_,\_\_,\_\_,\_\_$$

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Meta:

Again, the answer to this puzzle is a single word that fits into the blanks above.

Moved from previous hint: the answer should not only describe the location but simultaneously also alleviate my worries.

This puzzle should be more straightforward than my first one.

Hint 1 (read if you think this puzzle will be tedious, because it's not):

How absentminded am I? Before I left the US, I entered my PIN number wrong so many times at the ATM machine it locked me out! I'm so forgetful... wait, when did I leave for this trip again? That's such an important date, you'd think I'd remember it...

Hint 2 (read this if a certain thing is ambiguous):

If you're wondering, yes, it is the center of gravity. Also, high school physics classes used two decimal places, so it'll work for us too.

Hint 3 (spoilers):

Think you're on the edge of the getting the answer? Yes, yes you are. Think you've triangulated my position? Make sure it's got something in common with the first letter of every sentence.

Answer

Final answer! You are in:

the district of Chomutov in the Czech Republic near the border with Germany.

The eight-letter word is:

Schengen which alleviates your worries because the two countries are part of the Schengen Agreement and crossing the border should be easy.

The decoding starts with:

the codes below each book. They look like geodetic coordinates (latitude and longitude). As the date is the 13th and the coordinates use digits from 1-9-A-D, it seems that each book's ISBN-13 is needed. The following coordinates result from a 13 digit substitution key of 123456789ABCD:

First ISBN 9781559402736 with (D8.46,-A4.1C) $\Rightarrow$ (64.15,-21.93) at Reykjavik, Iceland

Second ISBN 9780684801223 with (D5.22,D.CB) $\Rightarrow$ (36.77,3.22) at Algiers, Algeria

Third ISBN 9780446310789 with (59.24,56.C4) $\Rightarrow$ (41.70,44.80) at Tbilisi, Georgia

Each of these locations are capital cities. A capital is "common with the first letter of every sentence".

Using geomidpoint.com,

the center of gravity of these three coordinates is (50.54,13.25) which is located in the Czech Republic near the border with Germany.