I did this in my place about a year ago, i was going threw the same thing yall are (excuse that but its in my nature). Anyways, i first looked at the bookcase option and discovered one..problem. A very big problem actually...it was typical. A intruder with the intent to rob you, who has half of a brain, will check bookcases because people have been known to use them to hide safes or rooms. So i came up with a rather different idea, and then i had a police friend try to find it and he failed. The idea is simple...use something in a place that looks normal. My application was thus, right between a large walk-in closet and a bathroom (the walk in closet was shrunk in size to make this hidden room) was what seemed like a large vanity mirror. Ok..closet..mirror..normal enough, EXACTLY!. That mirror was actually 2 things. First it was actually a mirror that could only be seen threw from one side, and the other side looked like a regular mirror (like a police station interogation room mirror). Second it was the outer door/cover for the door to the hidden room.Mirrors are a real pain to attach anything to, so i had to come up with something, and i did. I mounted the mirror on a 1/8 thick peice of plywood that extended past the edges of the mirror just enough to mount molding on. So far so good. The molding was specially cut to fit flush to the wall but yet still be attached to the plywood backing. So now i had basically a really fancy mirror. I used a simple paino type hinge (long and with alot of screw holes..the screws couldnt be that long so there were going to have to be alot of them)but i had a small part of the plywood cut out so that i could attach the hinge and have it be not noticable (that was a bit tricky). Before i did that, i thought about where to attach the hinge..3 sides were possible, left right and top. I choose the top only because it was easier to conceal the hinge. Next problem..opening a dang mirror that weighed a good 20 lbs on a hinge that was 2 ft long and rated for 15 lbs..yeh problem. Well in the closed position no problem..the ground helped support the mirror(i made it flush with the ground). But i couldnt open it or it would rip off the hinge and fall..on me...not good. IDEA!..and a very nice one too. Springs..expansion ones to be exact. The type that expand when they are allowed to. I set it up so i had 2 springs..rather light weight ones, but between them they would add another 10 lbs of carring weight to the hinge..perfect. Now one problem remained..lockage. I came up with a really..weird idea. I hand built a device that was mounted under the carpet (the outside of the room..the main living room..was carpeted). You had to step on the device to unlock the door...totally concealed. In the end..and after about..7 hours of work(this is not an easy job) it was working..well the outer door was at least, the outer door was the important part because it concealed it all. The inner door was simple..a standard door..sorta. It was a standard door except i mounted it sans frame, just straight to the studs, and right flush with the wall..hence flush with the back of the mirror door device. This door has a lock too..a very..old one. Since it was flush there couldnt be any doorhandle or anything protruding..dead give away. I happened to be watching one of these home improvement shows..and saw my answer. The old style flush fitting locks with the weird keys, they are still made for those that want to "capture" the old house feel. Well i got one that acted as a deadbolt..so no handle. One small issue, the thing wasnt entirely flush..it came out about 1/16 of an inch, so i chiseled out of the actual door that much and mounted the lock..making it flush. It now worked. The outer door looked like a vanity mirror positioned next to a walk in closet..very normal. The lock to it was hidden..great. The inner door was mounted flush..great for defeating the old "knock on it to see if its hollow" idea, and has its own lock. I use the room as a weapons locker, i collect medieval swords and axs along with new firearms. The best part, which is why i have installed that mirror that can be seen out of 1 way, that was was out from the hidden room, is now when im in that room i can keep the secondary door open, the primary door(mirror) closed and still watch what is going on in the house. Call it voyuerism if you like, i call it making a hidden room for my valuables and having the ablitily to see if some idiot breaks in while im in there..which would be stupid to say the least.
Anyways..I hoped this helped and it should have given yall another way of looking at things.