diff --git a/kcc/kindlesplit.py b/kcc/kindlesplit.py
index fac6253..26e017f 100644
--- a/kcc/kindlesplit.py
+++ b/kcc/kindlesplit.py
@@ -100,11 +100,11 @@ def nullsection(datain, secno):  # make it zero-length without deleting it
         datalst.append(struct.pack('>L', ofs) + struct.pack('>L', flgval))
     lpad = zerosecstart - (first_pdb_record + 8*nsec)
     if lpad > 0:
-        datalst.append('\0' * lpad)
+        datalst.append(b'\0' * lpad)
     datalst.append(datain[zerosecstart: secstart])
     datalst.append(datain[secend:])
-    dataout = "".join(str(datalst)[1:-1])
-    return dataout.encode('utf-8')
+    dataout = b"".join(datalst)
+    return dataout
 
 
 def deletesectionrange(datain, firstsec, lastsec):  # delete a range of sections
@@ -130,11 +130,11 @@ def deletesectionrange(datain, firstsec, lastsec):  # delete a range of sections
         datalst.append(struct.pack('>L', ofs) + struct.pack('>L', flgval))
     lpad = newstart - (first_pdb_record + 8*(nsec - (lastsec - firstsec + 1)))
     if lpad > 0:
-        datalst.append('\0' * lpad)
+        datalst.append(b'\0' * lpad)
     datalst.append(datain[zerosecstart:firstsecstart])
     datalst.append(datain[lastsecend:])
-    dataout = "".join(str(datalst)[1:-1])
-    return dataout.encode('utf-8')
+    dataout = b"".join(datalst)
+    return dataout
 
 
 def insertsection(datain, secno, secdata):  # insert a new section
@@ -160,18 +160,17 @@ def insertsection(datain, secno, secdata):  # insert a new section
         datalst.append(struct.pack('>L', ofs) + struct.pack('>L', flgval))
     lpad = newstart - (first_pdb_record + 8*(nsec + 1))
     if lpad > 0:
-        datalst.append('\0' * lpad)
+        datalst.append(b'\0' * lpad)
     datalst.append(datain[zerosecstart:secstart])
     datalst.append(secdata)
     datalst.append(datain[secstart:])
-    dataout = "".join(str(datalst)[1:-1])
-    return dataout.encode('utf-8')
+    dataout = b"".join(datalst)
+    return dataout
 
 
 def insertsectionrange(sectionsource, firstsec, lastsec, sectiontarget, targetsec):  # insert a range of sections
     dataout = sectiontarget
     for idx in range(lastsec, firstsec-1, -1):
-        print(dataout)
         dataout = insertsection(dataout, targetsec, readsection(sectionsource, idx))
     return dataout
 
@@ -287,7 +286,7 @@ class mobi_split:
                 # datain_rec0 = del_exth(datain_rec0,534)
                 # don't remove the EXTH 125 KF8 Count of Resources, seems to be present in mobi6 files as well
                 # set the EXTH 129 KF8 Masthead / Cover Image string to the null string
-                datain_rec0 = write_exth(datain_rec0, 129, '')
+                datain_rec0 = write_exth(datain_rec0, 129, b'')
                 # don't remove the EXTH 131 KF8 Unidentified Count, seems to be present in mobi6 files as well
 
                 # Make sure we have an ASIN & cdeType set...