When sorting the book list on text fields like title, recognize numbers inside the text and sort them as number. So the text 'Book 2' will sort before 'Book 100'. If you prefer the old behavior, you can restore it via Preferences->Tweaks. Fixes #1132025 (Incorrect sort when title contains numbers)

resources/default_tweaks.py

@@ -517,3 +517,11 @@ default_tweak_format = None
 # your library and your personal editing style.
 preselect_first_completion = False
 
+#: Recognize numbers inside text when sorting
+# This means that when sorting on text fields like title the text "Book 2"
+# will sort before the text "Book 100". This is how humans usually expect
+# things to sort. If you prefer the computer sort (which is a little faster,
+# but will cause Book 100 to sort before Book 2), then set numeric_collation
+# to False.
+numeric_collation = True
+

src/calibre/utils/icu.c

@@ -59,6 +59,7 @@ icu_Collator_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         PyErr_SetString(PyExc_Exception, "Failed to create collator.");
         return NULL;
     }
+    ucol_setAttribute(collator, UCOL_NUMERIC_COLLATION, UCOL_ON, &status);
 
     self = (icu_Collator *)type->tp_alloc(type, 0);
     if (self != NULL) {
@@ -110,6 +111,21 @@ icu_Collator_set_strength(icu_Collator *self, PyObject *val, void *closure) {
 }
 // }}}
 
+// Collator.numeric {{{
+static PyObject *
+icu_Collator_get_numeric(icu_Collator *self, void *closure) {
+    UErrorCode status = U_ZERO_ERROR;
+    return Py_BuildValue("O", (ucol_getAttribute(self->collator, UCOL_NUMERIC_COLLATION, &status) == UCOL_ON) ? Py_True : Py_False);
+}
+
+static int
+icu_Collator_set_numeric(icu_Collator *self, PyObject *val, void *closure) {
+    UErrorCode status = U_ZERO_ERROR;
+    ucol_setAttribute(self->collator, UCOL_NUMERIC_COLLATION, (PyObject_IsTrue(val)) ? UCOL_ON : UCOL_OFF, &status);
+    return 0;
+}
+// }}}
+
 // Collator.actual_locale {{{
 static PyObject *
 icu_Collator_actual_locale(icu_Collator *self, void *closure) {
@@ -415,6 +431,10 @@ static PyGetSetDef  icu_Collator_getsetters[] = {
      (char *)"The strength of this collator.",
      NULL},
 
+    {(char *)"numeric",
+     (getter)icu_Collator_get_numeric, (setter)icu_Collator_set_numeric,
+     (char *)"If True the collator sorts contiguous digits as numbers rather than strings, so 2 will sort before 10.",
+     NULL},
 
     {NULL}  /* Sentinel */
 };

src/calibre/utils/icu.py

@@ -46,6 +46,8 @@ def load_collator():
         icu = load_icu()
         if icu is not None:
             _collator = icu.Collator(get_locale())
+            if not tweaks['numeric_collation']:
+                _collator.numeric = False
     return _collator
 
 def primary_collator():