diff --git a/tablib/formats/_json.py b/tablib/formats/_json.py
index d60cd21..c2dd524 100644
--- a/tablib/formats/_json.py
+++ b/tablib/formats/_json.py
@@ -24,14 +24,12 @@ def import_set(dset, in_stream):
 	dset.dict = json.loads(in_stream)
 
 
-def import_book(in_stream):
+def import_book(dbook, in_stream):
 	"""Returns databook from JSON stream."""
 
-	book = tablib.core.Databook()
+	dbook.wipe()
 	for sheet in json.loads(in_stream):
 		data = tablib.core.Dataset()
 		data.title = sheet['title']
 		data.dict = sheet['data']
-		book.add_sheet(data)
-	
-	return book
\ No newline at end of file
+		dbook.add_sheet(data)
diff --git a/tablib/formats/_yaml.py b/tablib/formats/_yaml.py
index 74d9155..665e06d 100644
--- a/tablib/formats/_yaml.py
+++ b/tablib/formats/_yaml.py
@@ -25,14 +25,13 @@ def import_set(dset, in_stream):
 	dset.dict = yaml.load(in_stream)
 
 
-def import_book(in_stream):
+def import_book(dbook, in_stream):
 	"""Returns databook from YAML stream."""
 
-	book = tablib.core.Databook()
+	dbook.wipe()
+
 	for sheet in yaml.load(in_stream):
 		data = tablib.core.Dataset()
 		data.title = sheet['title']
 		data.dict = sheet['data']
-		book.add_sheet(data)
-
-	return book
\ No newline at end of file
+		dbook.add_sheet(data)
\ No newline at end of file