Land of the Undying?
 

Is there any book that talks about this land? What is it?

Aman, the "Undying land" is the land that is inhabited by the Ainur and the Maia (with a few exceptions). A great meny elves dwell there too.

It used to be an island over the western sea. However after Ar-Phazron's rebellion it was taken off the face of the earth t be somewhere outside of middle earth.

All this information is in the silmarillion, which I believe is the book you are looking for.

The Silmarillion is the best place to find out about it, also there are a few threads in here that talk about it too.

It wasn't actually in Middle-Earth. Middle Earth is one continent on the face of the world of Arda -- our 'Earth'.
Aman, the main body of the Undying Lands, is the oher continent, and similarly sized. I think it's still in the world, only there is a sort of enchantment around it to prevent Men from entering.

I remember something about after Numenor attacked the west, the Valar laid down their gaurd and Eru removed the Undying Lands from the confines of the world. Something like that. I think the enchantment was the protection it had prior to that.

'The world was diminished' certainly suggests the Undying Lands were no longer physically a part of the world after the Downfall.

If it wasn't in the world, where else would it be? Perhaps it was still in the world from the point of view of those who dwelled there, but not from the point of view of Men in ME. If you follow me. Sort of another dimension.

Aman and Tol Eressea were indeed removed from the world and can only be reached via the Straight Road whereas all other "roads" on Earth are "curved", i.e. a ship can only circle the globe unless it enters the Straight Road. Elves entered the Straight Road in specially hallowed ships which departed at dusk. The ships of men could enter the Straight Road only via some unusual chance or fate, if at all. In Letters, JRRT goes on to say that once in the West, there is no return to Middle Earth except with the assistance of the Valar.

I always imagine Arda before as a big disc or pancake, where Aman is in the uttermost West. Around this disc there were the Outer ocean which was made a globe of water (Aman touched the outer ocean in the West. After the Downfall of Numenor every part of the pancake except Aman was bent to a globe admidst the 'englobing' Outer Ocean. Aman remained in the excact same position as it always had been only now it was 'hidden' in come veil of enchantment. (If it hadn't Aman woulc look like a Very Very BIG continent floating casually in the air - a sight mst men wouldn't be able to cope with - so to reduce the number of mental problems on 'earth' it was 'hidden'... ) [img]smilies/wink.gif[/img]

The world (according to Tolkien) did start as a disk and had it's form changed. The Undying lands were absolutely removed from the physical world (not just hidden as it was in the First & Second Ages).

- Cirdan / Maglor

The undying lands were removed beyond the circles of the world.

Exactly. Beyond the circles of the world, but not the straights of the world.

If it enters the Straight Road, it enters another dimension within this world, I should say.

To the Valar, the Undying Lands are still within the World. If Valinor is in the middle of the Atlantic, say, and a ship sets out west from it, it would reach the West coast of Europe or Africa, as long as the Valar consented it be so. Otherwise the ship would inexplicably find itself heading back towards Valinor again. (This is my theory.) But if a ship of Men set out on a path that would bring it straight to Valinor, then it would travel a 'bent path', perhaps around the Undying Lands or right through them without ever knowing they were there. Satellite images don't pick them up, similar to the way a vampire cannot be seen in a mirror. But from Valinor itself the story is different.
Do you catch my meaning?