"Invalid book tag" given because of this

public class Guide
{
    public static ItemStack guideBook()
    {
        ItemStack guideBook = new ItemStack(Items.written_book, 1);
        guideBook.setTagCompound(new NBTTagCompound());
        guideBook.getTagCompound().setString("title", StatCollector.translateToLocal("book.title"));
        guideBook.getTagCompound().setString("author", "Version: " + VTweaks.version);
        NBTTagList pages = new NBTTagList();

        ArrayList<String> indiPages = new ArrayList<String>();

        indiPages.add("Hi :)");

        for (String s : indiPages)
            pages.appendTag(new NBTTagString(s));

        guideBook.getTagCompound().setTag("pages", pages);

        return guideBook;
    }