项目下的urls.py
from django.conf.urls import url,include

urlpatterns = [
    url(r'^BookApp/', include('BookApp.urls')),
]

app下的urls.py
from django.conf.urls import url

from . import views
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^indexBook/$', views.indexBook),
]

访问时应该是访问 /BookApp/indexBook/　

STATICFILES_DIRS = [
    os.path.join(BASE_DIR, 'BookApp', 'static')
]

<link rel="stylesheet" href="/static/plugins/bootstrap/css/bootstrap.min.css">