So how did the bookies do?

Predictions are only as good as their accuracy.

So how did the bookies predictions turn out?

Not very good, if we consider an accurate prediction to be within 2 percentage points, and a close prediction to be within 5 percentage points, and anything above 7 percentage points to be off the mark.

The "bookies' prediction" had 3 accurate calls (Ang Mo Kio GRC, Tampines GRC, and Marsiling-Yew Tee GRC), and 4 close predictions (Chua Chu Kang, Pasir Ris-Punggol, Nee Soon GRCs, and Bt Panjang SMC).

However, they had 5 "Epic Fails" where they predicted the wrong candidate/party would win.

Comparing their Predictions with the final Results.
Ang Mo Kio GRC - Accurate!

Prediction:       PAP-79.4%,    RP-20.6%

Final Results:  PAP- 78.63%, RP-21.37%

Aljunied GRC - FAIL!

Prediction:      WP-60.9% ,  PAP-39.1%

Final Result:   WP-50.95%, PAP-49.05%

WP still won, but by a hair, not the comfortable margin predicted.

Sembawang GRC - Way Off!

Prediction:    PAP-58.4% ,  NSP-41.6% 

Final Result: PAP-72.28%, NSP-27.72%

PAP won by a landslide. Not the marginal but comfortable win predicted.

Bishan- Toa Payoh GRC - Way Off!

Prediction:    PAP-60.6%,   SPP-39.4%

Final Result: PAP-73.59%, SPP-26.41%

PAP won by a landslide. Not the comfortable win predicted.

Pasir Ris -Punggol GRC - Close!

Prediction:    PAP-77.4%,    SDA-22.6% 

Final Result: PAP- 72.89%, SDA-27.11%

Prediction was more optimistic (for PAP) or pessimistic (for SDA), but was close to final result.

Jurong GRC - Way Off!

Prediction:    PAP-68.7% , SingFirst-31.3%
Final Result: PAP-79.28%, SingFirst 20.72%

Prediction was more than 10 percentage points off.

Marine Parade GRC - Off!

Prediction:    PAP-54.2% , WP-45.8%

Final Result: PAP-64.07%, 35.93%

Prediction was 10 percentage points off.

Nee Soon GRC - Quite Close.

Prediction:    PAP-60.3% , WP-39.7% (PAP wins)

Final Result: PAP-66.83%, WP-33.17%

A bit pessimistic (For PAP), but quite close (6 percentage points).

Tampines GRC - Accurate!

Prediction :   PAP-74.4%,   NSP-25.6% 

Final Result: PAP-72.06%, NSP-27.94%

Tanjong Pagar GRC - Way Off!

Prediction :   PAP-61.2%,   SingFirst-38.8%

Final Result: PAP-77.71%, SingFirst-22.29%

Chua Chu Kang GRC - Close!

Prediction : PAP-71.8% , PPP-28.2%

Final Result: PAP-76.89, PPP-23.11%

East Coast GRC - EPIC FAIL!

Prediction:    PAP-46.2%,   WP-53.8% 

Final Result: PAP-60.73%, WP-39.27%

Holland-Bukit Timah GRC - Off!

Prediction :   PAP-58.7%,   SDP-41.3% 

Final Result: PAP-66.62%, SDP-33.38%

West Coast GRC - Off!

Prediction :   PAP-68.6%,   RP-31.4%

Final Result: PAP 78.57%,  RP-21.43%

Marsiling-Yew Tee GRC - Accurate!

Prediction:    PAP-70.2%,   SDP-29.8%

Final Result: PAP-68.73%, SDP-31.27%

Jalan Besar GRC - Off!

Prediction:    PAP-58.1%,   WP-41.9% 

Final Result: PAP-67.73%, WP-32.27%

Radin Mas SMC - Way Off!

Prediction:    PAP-67.2%,   RP-31.2%,   Independent-1.6%

Final Result: PAP-77.25%, RP-12.71%, Independent-10.04%

Bukit Batok SMC - Way Off!

Prediction:    PAP-62.9%,   SDP-36.9%,   Independent-0.2%

Final Result: PAP-72.99%, SDP-26.40%, Independent-0.6%

MacPherson SMC - Off!

Prediction:    PAP-59.3%,   WP-39.6%, NSP-1.1% 

Final Result: PAP-65.58%, WP-33.6%, NSP-0.82%

Hong Kah North SMC - Way Off!

Prediction : PAP-61.3% , SPP-38.7%
Final Result: PAP-74.76%, SPP-25.24%

Bukit Panjang SMC - Close!

Prediction :   PAP-65.1%,    SDP-34.9%

Final Result: PAP- 68.38%, SDP-31.62%

Fengshan SMC - EPIC FAIL!

Prediction: PAP-45.8% , WP-54.2% 

Final Result: PAP-68.38%, WP-31.62%

Hougang SMC - Off!

Prediction: WP-65.4% , PAP-34.6%

Final Result: WP-57.69%, PAP-42.31%

Mountbatten SMC - Way Off!

Prediction :   PAP-56.4%,   SPP-43.6% 

Final Result: PAP-71.84%, SPP-28.16%

Pioneer SMC - Off!

Prediction :   PAP-67.6%,   NSP-32.4% 

Final Result: PAP-76.34%, NSP-23.66%

Potong Pasir SMC - EPIC FAIL!

Prediction: PAP-45.1% , SPP-54.9% 

Final Result: PAP-66.41%, SPP-33.59%

Punggol East SMC - EPIC FAIL!

Prediction :   WP-66.9%,   PAP-33.1%

Final Result: WP 48.24%, PAP-51.76%

Sengkang West SMC - EPIC FAIL!

Prediction : PAP-45.8% , WP-54.2% 

Final Result: PAP-62.11%, WP-37.89%

Yuhua SMC - Off!

Prediction : PAP-63.9% , SDP-36.1%

Final Result: PAP-73.54%, SDP-26.46%

On the one hand, you might say that the bookies were only "directionally wrong" in 5 cases. But if they are supposed to make odds based on the percentages, they were only close or accurate 7 times. Out of 29. 

I'm not a bookie and I do not know how one uses percentages like that, but I won't have any confidence with this type of results.