Although you can request multiple markets from listMarketBook, /wiki/spaces/BFAPIBETA/pages/1212460 and listMarketProfitandLoss, there are limits on the amount of data requested in one request.
...
sum(Weight) * number market ids must not exceed 200 points
/wiki/spaces/BFAPIBETA/pages/1212460 Data Weighting
| MarketProjection | Weight |
|---|---|
MARKET_DESCRIPTION | 1 |
RUNNER_DESCRIPTION | 0 |
| EVENT | 0 |
| EVENT_TYPE | 0 |
| COMPETITION | 0 |
| RUNNER_METADATA | 1 |
| MARKET_START_TIME | 0 |
listMarketBook Data Weighting
| PriceProjection | Weight |
| Null (No PriceProjection set) | 2 |
| SP_AVAILABLE | 3 |
| SP_TRADED | 7 |
| EX_BEST_OFFERS | 5 |
| EX_ALL_OFFERS | 17 |
| EX_TRADED | 17 |
listMarketProfitandLoss
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Data Weighting
| PriceProjection | Weight |
| Not applicable | 4 |
...