minor adjustments

- link to html and pdf version
- mention opening files if run in JupyterLab

Author: fangohr

book/index.ipynb

@@ -8,9 +8,12 @@
     "\n",
     "The content of [this book](https://github.com/fangohr/introduction-to-python-for-computational-science-and-engineering/blob/master/Readme.md) is distributed into chapters, using one Jupyter Notebook for each chapter.\n",
     "\n",
+    "You can read the book in different formats: [html](https://fangohr.github.io/introduction-to-python-for-computational-science-and-engineering/), [pdf](https://fangohr.github.io/introduction-to-python-for-computational-science-and-engineering/book.pdf), or you can use the [myBinder](https://mybinder.org/v2/gh/fangohr/introduction-to-python-for-computational-science-and-engineering/master?urlpath=tree/book/index.ipynb)\n",
+    " environment, in which you can read the text and execute the examples in a browser (without having to install Python locally) using one Jupyter notebook per chapter, as mentioned above.\n",
+    "\n",
     "If you have not used the Jupyter Notebook before, please read the section \"First steps with Jupyter Notebook\" below before you proceed.\n",
     "\n",
-    "If you are reading this online, and have started the interactive version using [myBinder](https://mybinder.org/v2/gh/fangohr/introduction-to-python-for-computational-science-and-engineering/master?urlpath=tree/book/index.ipynb), then you can use the menu `File` -> `Open ...` to open the different chapters as an executable notebook: this means you can execute and change all examples as you like.\n",
+    "If you are reading this online using the interactive [myBinder](https://mybinder.org/v2/gh/fangohr/introduction-to-python-for-computational-science-and-engineering/master?urlpath=tree/book/index.ipynb) environment, then you can use the menu `File` -> `Open ...` to open the different chapters as an executable notebook (in the classic Notebook), or by selecting the chapter in the panel on the left (in JupyterLab). In either case, you can execute, change, and re-execute all examples as you like. I believe this interactive exploration can be of great value as part of the learning process.\n",
     "\n",
     "*First steps with Jupyter Notebook*\n",
     "\n",
@@ -42,13 +45,6 @@
    "source": [
     "![Logo, created with MayaVi](static/images/mayavi/mayavi-samp.png \"3d magnetisation vector field\")\n"
    ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": []
   }
  ],
  "metadata": {