Starting off on API stuff.

MODSRC/vazkii/botania/api/BotaniaAPI.java

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+/**
+ * This class was created by <Vazkii>. It's distributed as
+ * part of the Botania Mod. Get the Source Code in github:
+ * https://github.com/Vazkii/Botania
+ * 
+ * Botania is Open Source and distributed under a
+ * Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License
+ * (http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_GB)
+ * 
+ * File Created @ [Jan 14, 2014, 6:15:28 PM (GMT)]
+ */
+package vazkii.botania.api;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public final class BotaniaAPI {
+
+	public static List<LexiconCategory> categories = new ArrayList();
+	
+	
+}

MODSRC/vazkii/botania/api/LexiconCategory.java

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+/**
+ * This class was created by <Vazkii>. It's distributed as
+ * part of the Botania Mod. Get the Source Code in github:
+ * https://github.com/Vazkii/Botania
+ * 
+ * Botania is Open Source and distributed under a
+ * Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License
+ * (http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_GB)
+ * 
+ * File Created @ [Jan 14, 2014, 6:23:47 PM (GMT)]
+ */
+package vazkii.botania.api;
+
+public final class LexiconCategory {
+
+	public final String tag;
+	
+	public LexiconCategory(String tag) {
+		this.tag = tag;
+	}
+	
+}

MODSRC/vazkii/botania/api/LexiconEntry.java

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+/**
+ * This class was created by <Vazkii>. It's distributed as
+ * part of the Botania Mod. Get the Source Code in github:
+ * https://github.com/Vazkii/Botania
+ * 
+ * Botania is Open Source and distributed under a
+ * Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License
+ * (http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_GB)
+ * 
+ * File Created @ [Jan 14, 2014, 6:17:06 PM (GMT)]
+ */
+package vazkii.botania.api;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import vazkii.botania.api.page.LexiconPage;
+
+public class LexiconEntry {
+	
+	public final String id;
+	public List<LexiconPage> pages = new ArrayList();
+	
+	public LexiconEntry(String id) {
+		this.id = id;
+	}
+	
+	public void setLexiconPages(LexiconPage... pages) {
+		this.pages.addAll(Arrays.asList(pages));
+	}
+	
+	public void addPage(LexiconPage page) {
+		pages.add(page);
+	}
+
+}

MODSRC/vazkii/botania/api/page/LexiconPage.java

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+/**
+ * This class was created by <Vazkii>. It's distributed as
+ * part of the Botania Mod. Get the Source Code in github:
+ * https://github.com/Vazkii/Botania
+ * 
+ * Botania is Open Source and distributed under a
+ * Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License
+ * (http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_GB)
+ * 
+ * File Created @ [Jan 14, 2014, 6:17:24 PM (GMT)]
+ */
+package vazkii.botania.api.page;
+
+import net.minecraft.client.gui.GuiScreen;
+
+public abstract class LexiconPage {
+	
+	public abstract void renderScreen(GuiScreen gui, int x, int y);
+
+}