diff --git a/cps/constants.py b/cps/constants.py
index 0736a354..3d1f0dfe 100644
--- a/cps/constants.py
+++ b/cps/constants.py
@@ -193,7 +193,7 @@ THUMBNAIL_TYPE_AUTHOR    = 3
 COVER_THUMBNAIL_ORIGINAL = 0
 COVER_THUMBNAIL_SMALL    = 1
 COVER_THUMBNAIL_MEDIUM   = 2
-COVER_THUMBNAIL_LARGE    = 3
+COVER_THUMBNAIL_LARGE    = 4
 
 # clean-up the module namespace
 del sys, os, namedtuple
diff --git a/cps/kobo.py b/cps/kobo.py
index 03fc29c3..3686c174 100644
--- a/cps/kobo.py
+++ b/cps/kobo.py
@@ -47,7 +47,7 @@ import requests
 from . import config, logger, kobo_auth, db, calibre_db, helper, shelf as shelf_lib, ub, csrf, kobo_sync_status
 from . import isoLanguages
 from .epub import get_epub_layout
-from .constants import COVER_THUMBNAIL_SMALL
+from .constants import COVER_THUMBNAIL_SMALL, COVER_THUMBNAIL_MEDIUM, COVER_THUMBNAIL_LARGE
 from .helper import get_download_link
 from .services import SyncToken as SyncToken
 from .web import download_required
@@ -903,7 +903,12 @@ def get_current_bookmark_response(current_bookmark):
 @requires_kobo_auth
 def HandleCoverImageRequest(book_uuid, width, height, Quality, isGreyscale):
     try:
-        resolution = None if int(height) > 1000 else COVER_THUMBNAIL_SMALL
+        if int(height) > 1000:
+            resolution = COVER_THUMBNAIL_LARGE
+        elif int(height) > 500:
+            resolution = COVER_THUMBNAIL_MEDIUM
+        else:
+            resolution = COVER_THUMBNAIL_SMALL
     except ValueError:
         log.error("Requested height %s of book %s is invalid" % (book_uuid, height))
         resolution = COVER_THUMBNAIL_SMALL
diff --git a/cps/shelf.py b/cps/shelf.py
index 6558e8d5..41d5ce1d 100644
--- a/cps/shelf.py
+++ b/cps/shelf.py
@@ -422,11 +422,14 @@ def render_show_shelf(shelf_type, shelf_id, page_no, sort_param):
     # check user is allowed to access shelf
     if shelf and check_shelf_view_permissions(shelf):
         if shelf_type == 1:
-            # order = [ub.BookShelf.order.asc()]
             if sort_param == 'pubnew':
                 change_shelf_order(shelf_id, [db.Books.pubdate.desc()])
             if sort_param == 'pubold':
                 change_shelf_order(shelf_id, [db.Books.pubdate])
+            if sort_param == 'shelfnew':
+                change_shelf_order(shelf_id, [ub.BookShelf.date_added.desc()])
+            if sort_param == 'shelfold':
+                change_shelf_order(shelf_id, [ub.BookShelf.date_added])
             if sort_param == 'abc':
                 change_shelf_order(shelf_id, [db.Books.sort])
             if sort_param == 'zyx':
@@ -453,7 +456,7 @@ def render_show_shelf(shelf_type, shelf_id, page_no, sort_param):
                                                            [ub.BookShelf.order.asc()],
                                                            True, config.config_read_column,
                                                            ub.BookShelf, ub.BookShelf.book_id == db.Books.id)
-        # delete chelf entries where book is not existent anymore, can happen if book is deleted outside calibre-web
+        # delete shelf entries where book is not existent anymore, can happen if book is deleted outside calibre-web
         wrong_entries = calibre_db.session.query(ub.BookShelf) \
             .join(db.Books, ub.BookShelf.book_id == db.Books.id, isouter=True) \
             .filter(db.Books.id == None).all()
diff --git a/cps/static/js/main.js b/cps/static/js/main.js
index 72f01867..2dbea6bc 100644
--- a/cps/static/js/main.js
+++ b/cps/static/js/main.js
@@ -612,6 +612,8 @@ $(function() {
         $("#auth_za").toggleClass("disabled");
         $("#pub_new").toggleClass("disabled");
         $("#pub_old").toggleClass("disabled");
+        $("#shelf_new").toggleClass("disabled");
+        $("#shelf_old").toggleClass("disabled");
         var alternative_text = $("#toggle_order_shelf").data('alt-text');
         $("#toggle_order_shelf").data('alt-text', $("#toggle_order_shelf").html());
         $("#toggle_order_shelf").html(alternative_text);
diff --git a/cps/tasks/thumbnail.py b/cps/tasks/thumbnail.py
index 2142b018..cc847274 100644
--- a/cps/tasks/thumbnail.py
+++ b/cps/tasks/thumbnail.py
@@ -35,7 +35,7 @@ except (ImportError, RuntimeError) as e:
 
 
 def get_resize_height(resolution):
-    return int(225 * resolution)
+    return int(255 * resolution)
 
 
 def get_resize_width(resolution, original_width, original_height):
@@ -72,7 +72,8 @@ class TaskGenerateCoverThumbnails(CalibreTask):
         self.cache = fs.FileSystem()
         self.resolutions = [
             constants.COVER_THUMBNAIL_SMALL,
-            constants.COVER_THUMBNAIL_MEDIUM
+            constants.COVER_THUMBNAIL_MEDIUM,
+            constants.COVER_THUMBNAIL_LARGE
         ]
 
     def run(self, worker_thread):
diff --git a/cps/templates/shelf.html b/cps/templates/shelf.html
index bf0b1ab4..d0fdb399 100644
--- a/cps/templates/shelf.html
+++ b/cps/templates/shelf.html
@@ -25,6 +25,8 @@
           <a data-toggle="tooltip" title="{{_('Sort authors in reverse alphabetical order')}}" id="auth_za" class="btn btn-primary disabled" href="{{url_for('shelf.show_shelf', shelf_id=shelf.id, sort_param='authza')}}"><span class="glyphicon glyphicon-user"></span><span class="glyphicon glyphicon-sort-by-alphabet-alt"></span></a>
           <a data-toggle="tooltip" title="{{_('Sort according to publishing date, newest first')}}" id="pub_new" class="btn btn-primary disabled" href="{{url_for('shelf.show_shelf', shelf_id=shelf.id, sort_param='pubnew')}}"><span class="glyphicon glyphicon-calendar"></span><span class="glyphicon glyphicon-sort-by-order"></span></a>
           <a data-toggle="tooltip" title="{{_('Sort according to publishing date, oldest first')}}" id="pub_old" class="btn btn-primary disabled" href="{{url_for('shelf.show_shelf', shelf_id=shelf.id, sort_param='pubold')}}"><span class="glyphicon glyphicon-calendar"></span><span class="glyphicon glyphicon-sort-by-order-alt"></span></a>
+          <a data-toggle="tooltip" title="{{_('Sort according to book added to shelf, newest first')}}" id="shelf_new" class="btn btn-primary disabled" href="{{url_for('shelf.show_shelf', shelf_id=shelf.id, sort_param='shelfnew')}}"><span class="glyphicon glyphicon-list"></span><span class="glyphicon glyphicon-sort-by-order"></span></a>
+          <a data-toggle="tooltip" title="{{_('Sort according to book added to shelf, oldest first')}}" id="shelf_old" class="btn btn-primary disabled" href="{{url_for('shelf.show_shelf', shelf_id=shelf.id, sort_param='shelfold')}}"><span class="glyphicon glyphicon-list"></span><span class="glyphicon glyphicon-sort-by-order-alt"></span></a>
         </div>
       {% endif %}
     {% endif %}
diff --git a/cps/ub.py b/cps/ub.py
index 5b889a72..0e15b8e2 100644
--- a/cps/ub.py
+++ b/cps/ub.py
@@ -311,7 +311,6 @@ class Anonymous(AnonymousUserMixin, UserBase):
         self.view_settings = data.view_settings
         self.kobo_only_shelves_sync = data.kobo_only_shelves_sync
 
-
     def role_admin(self):
         return False