The first one of anything always takes more time. I have done lots of bargellos and can tell you .... Just jump in... get the learning curve ( really not all that much)over with .. so you can move on to really enjoying just a new twist to strip piecing. If you can do strip piecing , you can do this! Her book has some that are more difficult than others... so I'm not sure which you are thinking about.
Starch your fabrics , it helps to keep everything going straight. I make a copy of the pattern , and take a marker or pencil and draw a line through the completed rows. Sometimes looking a the pattern it gets a bit confusing. Or take a sheet of paper and cover up the pattern of the row/column you just finished.
One of the benefits is they look harder than they really are.