diff --git a/zimui/src/services/collapse.ts b/zimui/src/services/collapse.ts
new file mode 100644
index 0000000..ddbb7b1
--- /dev/null
+++ b/zimui/src/services/collapse.ts
@@ -0,0 +1,65 @@
+/*
+Service to handle DOM manipulation to collapse subpages of books when there are too many
+
+See e.g. https://geo.libretexts.org/Courses/Fullerton_College (page ID 32303)
+*/
+
+const maxVisibleItems = 5
+
+class CollapseService {
+  handle_page_load() {
+    // Remove show all buttons which migth have been added previously
+    const previousShowAllButtons = document.querySelectorAll('button.zim-show-all-button')
+    for (const previousShowAllButton of previousShowAllButtons) {
+      previousShowAllButton.remove()
+    }
+
+    // Load all ul elements corresponding to a category (e.g. books)
+    const ulElements = document.querySelectorAll(
+      'div.mt-category-container dd.mt-listing-detailed-subpages ul'
+    )
+
+    for (const ulElement of ulElements) {
+      if (!ulElement.parentNode) {
+        continue // Failsafe, just in case
+      }
+      const listItems = ulElement.querySelectorAll('li')
+
+      // Check if there are more than 5 items
+      if (listItems.length <= maxVisibleItems) {
+        return
+      }
+
+      // Hide all list items after the 5th one
+      listItems.forEach((item, index) => {
+        if (index >= maxVisibleItems) {
+          item.style.display = 'none'
+        }
+      })
+
+      // Create the "Show all" button
+      const showAllButton = document.createElement('button')
+      showAllButton.className =
+        'mt-icon-expand-collapse mt-reveal-listing-expand-link zim-show-all-button'
+      showAllButton.title = 'Show all'
+
+      // Insert the button after the <ul> element
+      ulElement.parentNode.insertBefore(showAllButton, ulElement.nextSibling)
+
+      // Toggle visibility and text on button click
+      let isExpanded = false
+      showAllButton.addEventListener('click', function () {
+        isExpanded = !isExpanded
+        listItems.forEach((item, index) => {
+          item.style.display = isExpanded || index < maxVisibleItems ? '' : 'none'
+        })
+        showAllButton.title = isExpanded ? 'Show less' : 'Show all'
+      })
+    }
+  }
+}
+
+const collapseService = new CollapseService()
+Object.freeze(collapseService)
+
+export default collapseService
diff --git a/zimui/src/stores/main.ts b/zimui/src/stores/main.ts
index a17655b..45a0d91 100644
--- a/zimui/src/stores/main.ts
+++ b/zimui/src/stores/main.ts
@@ -2,6 +2,7 @@ import { defineStore } from 'pinia'
 import axios, { AxiosError } from 'axios'
 import type { PageContent, Shared, SharedPage } from '@/types/shared'
 import mathjaxService from '@/services/mathjax'
+import collapseService from '@/services/collapse'
 import { WebpMachine, detectWebpSupport } from 'webp-hero'
 
 export type RootState = {
@@ -80,6 +81,9 @@ export const useMainStore = defineStore('main', {
             webpMachine.polyfillDocument()
           }
         })
+        .then(() => {
+          collapseService.handle_page_load()
+        })
     },
     checkResponseObject(response: unknown, msg: string = '') {
       if (response === null || typeof response !== 'object') {