If you have read on a Kindle, you have probably met X-Ray. You press a name you no longer recognise and a panel tells you who they are, where they have appeared, and how they connect to everyone else. It is one of the genuinely good ideas in digital reading, and the first thing most people notice about it is how badly they want it for every other book they own.
Then they discover they cannot have it. This page explains why, what X-Ray is actually doing, and what the equivalent looks like for an EPUB sitting on your own shelf.
X-Ray is Amazon's feature, built into Kindle. Amazon indexes the book, finds the recurring people, places and terms, and builds you a reference panel you can open without leaving the page. The value is not that the information is rare — most of it is in the book you are holding. The value is that you do not have to go and find it. The interruption is three seconds instead of three minutes, and you do not lose the thread of the scene.
It works on books you buy from the Kindle store. That is not an oversight or a limitation waiting to be lifted; it is a consequence of how it is built. Amazon generates X-Ray from its own catalogue, for files delivered through its own store, inside its own reader.
Anything outside that path is outside X-Ray. A DRM-free EPUB from a publisher's own shop. A book from a library lending service. A file you side-loaded onto a device. An indie title sold direct. A book you bought years ago in a format that predates all of this. In every one of those cases the book is legitimately yours and the feature simply is not there.
This is the ordinary shape of a platform feature. It is very good, and it is available exactly where the platform is. If your reading lives in one store, that may never trouble you. If it does not, you have a gap that no setting will close.
There is a second way readers meet the edge of this feature, and it is the more confusing one, because the book came from the right store. You open the menu and X-Ray is greyed out, or it is not listed at all. The obvious conclusion is that something on your device has gone wrong.
Almost always nothing has. X-Ray is generated per title, one book at a time, and a great many titles have never had it built. Older books, small-press books, translations, reissues and plenty of novels that sell perfectly well simply do not have one. The feature is present on your device and absent from that book, which is not a fault and cannot be reported as one.
This is worth stating plainly, because the advice you will find says something else. Search for why X-Ray is not working and you are told to update your device software, restart it, re-download the file, or check that you are on the newest Paperwhite. Those steps fix the rare case where something really is stuck. They cannot fix the common one, because the missing piece is not on your device at all — it is an entry in Amazon's catalogue that was never generated for that title, and no setting on your side reaches it.
So the honest answer to "why is X-Ray greyed out" is usually: because this particular book does not have one, and nothing you do will change that. Which leaves you exactly where the reader with a book from another shop already was — four hundred pages in, a name you cannot place, and no reference to open.
There is a second problem, and it is the more interesting one, because it applies even when X-Ray is available to you.
A reference built from the whole book knows the whole book. It was generated in one pass over the finished text, which means the entry for a character contains what that character turns out to be. Careful design can hide some of that. It cannot change where the information came from.
So the reader who most needs a reference — someone four hundred pages into a long novel, meeting a name they last saw six hundred pages ago — is exactly the reader who has the most to lose by opening one. You want to be reminded who someone is. You do not want to be told what they become.
Inkspell is built for that gap. You upload an EPUB you already own — from any shop, any library, any format that ended up on your drive — and it builds the reference X-Ray would have built, for a book nobody else was going to build one for.
Then it does the part that changes the shape of the problem: every entry is generated against the chapter your bookmark is on, and stops there. A character's biography is written from the chapters you have read and no further. A recap ends exactly where you stopped. The relationship map shows the alliances that exist as far as you have got, not the ones that come later. Move your bookmark forward and more appears.
That is a different mechanism from hiding things, and it is worth being precise about the difference. The entry is not written and then filtered. It is written from a book that, as far as the entry is concerned, has not been finished yet.
One thing it deliberately is not: a bookstore. Inkspell sells no books, supplies no files and has no catalogue. You bring a book you already own, which is the only arrangement that makes sense for a tool whose entire job is to remember something you are in the middle of reading.
If your books all come from one store and that store already builds you a reference, use it — it is right there and it is good. This is for the reader whose library is scattered across shops, libraries and years, who has met X-Ray, wanted it for the book actually in front of them, and found it missing.
Get Inkspell on Google Play, or read why a fan wiki cannot do this job — the other place readers go when they have forgotten who someone is.