Add persistent linking books

README.md

@@ -4,10 +4,19 @@ Rivencraft is a clean, incremental port of the ideas and gameplay of
 [Mystcraft Legacy](https://github.com/Mystcraft/Mystcraft-Legacy) to Minecraft
 1.21.1 on NeoForge.
 
-The bootstrap milestone is complete. The project currently provides a valid
-NeoForge mod, a creative tab, and an unwritten Descriptive Book item. Age
-generation, linking, symbols, instability, and writing mechanics have not been
-ported yet.
+The bootstrap milestone is complete and books/linking is in progress. The
+project currently provides an unwritten Descriptive Book and a functional
+Linking Book with persistent, dimension-aware destinations and safe landing
+checks. Age generation, symbols, instability, and writing mechanics have not
+been ported yet.
+
+## Linking Book
+
+Craft a Linking Book from a vanilla book and an ender pearl. Sneak-right-click
+the unbound book to record the current location, then right-click it to return
+there. The destination is stored on the item and survives inventory and world
+saves. Travel only succeeds if the target dimension is loaded and a solid,
+collision-free landing position can be found nearby.
 
 ## Requirements